3.887.5275.200
Issue 1 - 2014
SMART HART® Pressure Transmitter
Series LD256
Installation and Maintenance Instructions
The PED Directive 97/23/EC is repealed and replaced by the new
PED Directive 2014/68/EU with effect from 19 July 2016.
The ATEX Directive 94/9/EC is repealed and replaced by the new
ATEX Directive 2014/34/EU with effect from 20 April 2016.
1. Safety information
2. General product information
3.Installation
4. Configuration
5. Spare parts
E X P E R T I S E
S O L U T I O N S
S U S T A I N A B I L I T Y
© Copyright 2014
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ATTENZIONE
Lavorare in sicurezza con apparecchiature
in ghisa e vapore
Working safely with cast iron products on steam
Informazioni di sicurezza supplementari - Additional Informations for safety
Lavorare in sicurezza con prodotti
in ghisa per linee vapore
I prodotti di ghisa sono comunemente presenti
in molti sistemi a vapore.
Se installati correttamente, in accordo alle
migliori pratiche ingegneristiche, sono dispositivi
totalmente sicuri.
Tuttavia la ghisa, a causa delle sue proprietà
meccaniche, è meno malleabile di altri materiali
come la ghisa sferoidale o l’acciaio al carbonio.
Di seguito sono indicate le migliori pratiche
ingegneristiche necessarie per evitare i colpi
d'ariete e garantire condizioni di lavoro sicure
sui sistemi a vapore.
Movimentazione in sicurezza
La ghisa è un materiale fragile: in caso di
caduta accidentale il prodotto in ghisa non è
più utilizzabile. Per informazioni più dettagliate
consultare il manuale d'istruzioni del prodotto.
Rimuovere la targhetta prima di effettuare la
messa in servizio.
Working safely with cast iron
products on steam
Cast iron products are commonly found on steam
and condensate systems.
If installed correctly using good steam
engineering practices, it is perfectly safe.
However, because of its mechanical properties,
it is less forgiving compared to other materials
such as SG iron or carbon steel.
The following are the good engineering practices required to prevent waterhammer and
ensure safe working conditions on a steam
system.
Safe Handling
Cast Iron is a brittle material. If the product is dropped
during installation and there is any risk of damage
the product should not be used unless it is fully
inspected and pressure tested by the manufacturer.
Please remove label before commissioning
Prevenzione dai colpi d’ariete - Prevention of water hammer
Scarico condensa nelle linee vapore - Steam trapping on steam mains:
Intervalli di 30÷50 m. intervals
Penden
za - Gra
Vapore
Steam
dient 1:1
00
Gruppo di scarico
Trap set
Condensa - Condasate
Penden
za - Gra
dient 1:1
Gruppo di scarico
Trap set
Condensa - Condasate
Esempi di esecuzioni corrette ( ) ed errate (
Steam Mains - Do's and Dont's:
Flusso
Flow
Vapore
Steam
00
Flusso
Flow
Vapore
Steam
Gruppo di scarico
Trap set
Condensa - Condasate
) sulle linee vapore:
Prevenzione delle sollecitazioni di trazione
Prevention of tensile stressing
Evitare il disallineamento delle tubazioni - Pipe misalignment:
Installazione dei prodotti o loro rimontaggio post-manutenzione:
Installing products or re-assembling after maintenance:
Evitare l’eccessivo serraggio.
Utilizzare le coppie di serraggio
raccomandate.
Do not over tighten.
Use correct torque figures.
Per garantire l’uniformità del carico e dell'allineamento,
i bulloni delle flange devono essere serrati in modo
graduale e in sequenza, come indicato in figura.
Flange bolts should be gradually tightened across
diameters to ensure even load and alignment.
Dilatazioni termiche - Thermal expansion:
Gli esempi mostrano l’uso corretto dei compensatori di dilatzione. Si consiglia di richiedere una
consulenza specialistica ai tecnici dell’azienda che produce i compensatori di dilatazione.
Examples showing the use of expansion bellows. It is highly recommended that expert advise is
sought from the bellows manufacturer.
Guide
Guides
Movimento assiale
Axial movement
Distanza breve
Short distance
Punto di fissaggio
Fixing point
Movimento assiale
Axial movement
Guide
Guides
Guide
Guides
Tiranti limitatori
Limit rods
Distanza
media
Medium
distance
Piccolo
movimento
laterale
Small
lateral
movement
Ampio
movimento
laterale
Large
lateral
movement
Punto di fissaggio
Fixing point
Tiranti limitatori
Limit rods
Guide
Guides
Piccolo
movimento
laterale
Small
lateral
movement
Ampio
movimento
laterale
Large
lateral
movement
1. Safety information
Safe operation of these products can only be guaranteed if they are properly installed, commissioned, used and maintained by qualified personnel (see Section 1.11 on this document) in compliance
with the operating instructions. General installation and safety instructions for pipeline and plant
construction, as well as the proper use of tools and safety equipment must also be complied with.
1.1 Intended use
The trasmitters object of the present instructions comply with the directive ATEX 94/9/CE and are
characterized by the following motodhds of protection:
II 1G Ex ia IIC T6
They are suitable for installation in Zone 0, Zone 1, Zone 2.
For connections and installation refer to this manual.
1.2Access
Ensure safe access and if necessary a safe working platform (suitably guarded) before attempting
to work on the product. Arrange suitable lifting gear if required.
1.3Lighting
Ensure adequate lighting, particularly where detailed or intricate work is required.
1.4 Hazardous liquids or gases in the pipeline
Consider what is in the pipeline or what may have been in the pipeline at some previous time. Consider: flammable materials, substances hazardous to health, extremes of temperature.
1.5 Hazardous environment around the product
Consider: explosion risk areas, lack of oxygen (e.g. tanks, pits), dangerous gases, extremes of
temperature, hot surfaces, fire hazard (e.g. during welding), excessive noise, moving machinery.
1.6 The system
Consider the effect on the complete system of the work proposed. Will any proposed action (e.g.
closing isolation valves, electrical isolation) put any other part of the system or any personnel at risk?
Dangers might include isolation of vents or protective devices or the rendering ineffective of controls
or alarms. Ensure isolation valves are turned on and off in a gradual way to avoid system shocks.
1.7 Pressure systems
Ensure that any pressure is isolated and safely vented to atmospheric pressure. Consider double
isolation (double block and bleed) and the locking or labelling of closed valves. Do not assume that
the system has depressurised even when the pressure gauge indicates zero.
1.8Temperature
Allow time for temperature to normalise after isolation to avoid danger of burns.
1.9 Tools and consumables
Before starting work ensure that you have suitable tools and/or consumables available. Use only
genuine Spirax Sarco replacement parts.
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1.10 Protective clothing
Consider whether you and/or others in the vicinity require any protective clothing to protect against
the hazards of, for example, chemicals, high /low temperature, radiation, noise, falling objects, and
dangers to eyes and face.
1.11 Permits to work
All work must be carried out or be supervised by a suitably competent person. Installation and
operating personnel should be trained in the correct use of the product according to the Installation
and Maintenance Instructions.
Where a formal ‘permit to work’ system is in force it must be complied with. Where there is no such
system, it is recommended that a responsible person should know what work is going on and, where
necessary, arrange to have an assistant whose primary responsibility is safety.
Post ‘warning notices’ if necessary.
1.12 Electrical work
Before starting work study the wiring diagram and wiring instructions and note any special requirements.
Consider particulary: mains supply voltage and phase, local mains isolation, fuse requirements,
earthing, special cables, cable entries / cable glands, electrical screening .
1.13Commissioning
Ater installation or maintenance ensure that the system is fully fuctioning.
Carry out test on many alarms or protective devices.
1.14Disposal
Unwanted equipment should be disposed of in a safe manner.
1.15 Returning products
Customers and stockists are reminded that under EC Health, Safety and Environment Law, when
returning products to Spirax Sarco they must provide information on any hazards and the precautions
to be taken due to contamination residues or mechanical damage which may present a health, safety
or environmental risk. This information must be provided in writing including Health and Safety data
sheets relating to any substances identified as hazardous or potentially hazardous.
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2. General product information
Main dimensions and sensor's reference
Cod.
Nom. Range
bar
Span
min/max
bar
Range Limits
min/max
bar
Overpressure
(max bar)
D
0/0,35
0,022/0,35
-0,35/0,35
2
E
0/1
0,06/1
-1/1
6
F
0/2,5
0,156/2,5
-1/2,5
10
G
0/5
0,31/5
-1/5
16
H
0/10
0,625/10
-1/10
30
K
0/30
1,875/30
-1/30
75
L
0/100
6,25/100
-1/100
150
M
0/200
12,5/200
-1/200
500
N
0/400
25/400
-1/400
600
M20x1,5
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Product Sheet
Overview
LD256 series SMART pressure transmitters are microprocessor based instruments that combine
the analog signal advantages (4-20mA) together with the flexibility of digital communication using
HART® protocol. They can be remotely configured by a universal hand held terminal (HHT).
Moreover, it is possible to locally configure the instruments (zero and span) by means of 2 pushbuttons and to display the data on the wide LCD display. The LD256 transmitters, complete with
diaphragm in AISI 316, measure relative pressure with spans from 0,022 to 400 bar. The pressure
measuring element is a piezoresitive sensor. It is possible to choose a variety of sensors to satisfy
all process conditions. The Spirax Sarco measuring cell contains the sensor and transmits pressure
to the electronics. Thermal drift is compensated using the temperature signal generated by a PTC
thermistor integrated in the sensor itself. Based on these readings the microprocessor generates
the 4-20mA analog output "two wires system" and displays the pressure measurement on the LCD.
Some of the main characteristics of this microprocessor-based transmitter, are:
- Wide rangeability.
- Automatic temperature compensation.
- Digital communication using HART® protocol.
Functional Data
With reference to the following, please note these definitions:
Nominal range: (referred to the sensor mounted in the instrument) the measured pressure range
for which the sensor has been designed. Defined as a minimum and maximum value.
Nominal span: the interval between the minimum and maximum values of the sensor nominal
range. The span is a single number.
Measuring range: the minimum and maximum range values for which the transmitter is to be calibrated.
Measuring span: the interval between minimum and maximum values of the measuring range.
Input scale initial value or zero input: minimum pressure value within in the measuring range.
Input full scale value: maximum pressure value within in the measuring range.
Transmitter parameters
The parameters that are available for display and setting are:
Measuring span: possibility to change from 6,25% to 100% of the nominal span.
Zero adjustment: digital calibration ± 15%.
Linearity adjustment: 8 points within the nominal range.
Low/upper range values: they can be set within the nominal range provided that the span greater
than minimum span.
Damping: digitally adjustable from 0 to 15 sec. (minimum response time ~ 0,1 sec.).
Reverse output: automatically obtained via software.
Transfer function: linear/square root via software.
Self test: in case of malfunction the analog output is forced to the fail-safe state of 3,8mA or 23,2mA.
Measuring units: 14 different pressure units or % of the measuring span, selectable via software.
Physical characteristics
Power supply: 12,5-30 Vdc with no load
Output signal:
Analog 4-20mA, 2 wires.
Digital using HART®
Ambient Conditions
Temperature
Process fluid: -60 ÷ +85°C (with finned arm max 150°C)
Housing: -40 ÷ +85°C
Handling and storage: -40 ÷ +90°C
Relative Humidity: 0 a 100% R.H.
LCD display reading: -10 ÷ +70°C
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Performances
Unless otherwise stated the performance specifications refer to ambient temperature = 20°C and
nominal span. Unless otherwise stated, all errors are shown as a percentage of nominal span
Accuracy rating: guaranteed within the following limits:
Resolution: ± 0,01%.
Accuracy: ± 0,1% including non linearity, repeatability and hysteresis errors.
Dead band: negligible.
Influence of Operating conditions
Thermal drift: referred to -10 ÷ +65°C range.
Zero: ± 0,1%/10°K. Span: ± 0,1%/10°K at nominal range.
Power supply effect: Negligible between 12,5 and 30 V d.c.
Physical specifications
Process wetted parts: Diaphragm in AISI 316 L/Hastelloy C - process chambers, adapters, drain
and vent plugs AISI 316 - gaskets PTFE + Viton + bolts carbon steel / AISI 304.
Housing: die cast aluminium alloy AL UNI 3571 finished with epoxy resin (RAL 5010).
Filling fluid: silicone oil.
Nameplate: stainless steel, fixed on housing.
Calibration
Standard: at nominal range, direct action.
Optional: at the conditions specified with the order.
Environmental protection: the transmitter is dust and sand tight and protected against sea waves
effects as defined by IEC IP 66. Suitable for tropical climate operation as defined in DIN 50.015.
Process connections: ½" NPT M.
Electrical connections: two entries on electronic housing, M20 x 1,5 and cable gland PG 13,5 for 7
to 12mm diameter cable.
Terminal board: 2 terminals for signal wiring up to 1,5 mm2 (14 AWG). Connection for ground and
cable shield.
Mounting position: any position.
Net weight: 1.4 kg. approx.
Explosion Protection
Equipment and protection system ATEX 94/9/CE
Intrinsically safety
Ex ia IIC T6 with Tamb -40 °C ÷ +60°C
Ex ia IIC T5 with Tamb -40 °C ÷ +75°C
Group II class 1G suitable for zone 0,1,2 - EN60079-10.
Electromagnetic Compatibility
Conforms to the standard CEI EN 61326-1 (1997) in accordance with 89/336/EEC and following
modifications.
Pressure
source
Indicator
Test gauge
Power
supply
Bench Calibration Set-up
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Standard specifications
The electronic transmitters Series LD256 are described in Products Sheet 7E.171. In these data
sheets information can be found on: Functional Data - Operating Conditions - Performances - Operating Influences - Physical Specifications - Certificates - Codification - Dimensions.
Overview
LD256 series transmitters measure relative pressure in ranges from 22 mbar up to 400 bar.
The pressure measuring element is a piezoresistive sensor. It Is possible to choose between
sensors to satisfy the process conditions. The Spirax Sarco's Measuring Cell generates a signal
corresponding to the actual pressure and is completed with a PTC thermistor which also transmits
the temperature of the measuring cell to the electronic system. On the basis of these two values and
of the configurated parameters the microprocessor based electronics (Fig. 1) generates a standard
output signal (4 to 20 mA, Iwo wires system) and displays the measurement on the LCD. Moreover
LD256 transmitters contain (depending on Hw and SW release) a PID (Proportional, Integral, Derivative) Control algorithm that allows to use the 4 to 20 Ma.
The functional block diaphragm of the transmitter is shown in the figure below.
Fig. 1 - Block Diagram
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3. Installation
3.1 Instrument Identification
Instrument data can be found on the nameplate fixed to the top of transmitter housing. The Serial
Number that must be quoted at the occurrence of specific requests to the manufacturer. Fig.2 shows
both sides of the housing with covers removed.
Front:
Electronic Module
Nut
Back
Fig. 2 - LD256 Series top work
Fig. 3 - Mounting
3.2 Transmitter mounting
The transmitters LD256 are supplied for direct mounting.
- Check whether instrument’s operating conditions are within the limits as reported in the technical
specifications sheets and/or label.
-Make sure that the operating conditions are compatible with the specification given to the manufacturer.
- Never install standard instrument under the sun or in any other location which could cause direct
overheating through radiation.
- For measurement in the presence of particularly hot liquids (e.g. steam) install the instrument
on a siphon (as in the case of manometers) or make sure that the instrument is supplied with a
suitable seal.
-For viscous liquids or those containing solid particles in suspension make sure that the connection
to the process is a suitable one in order to avoid clogs.
-Pressure transmitters are calibrated upright with sensors turned down (unless otherwise specified).
Any different position introduces a variation of output zero value. Maximum variation (offset) is
equivalent to 20mmH2O in pressure.
Refer to dimensional drawing for details, the position of the housing has no effect on the instrument
operation. In particular, before shipping the instrument is locked (Fig. 3). To obtain a good orientation
of the case it is necessary to unscrew the stop nut placed under the case. Turn the case in the new
position and screw the nut again.
3.3 Electrical connection
Under the rear cap are placed the terminals reporting the electric polarity (+/-). Insert the power supply
cable in to the housing through one of the two M20 x 1,5 openings. Device is protected from accidental
inversion of polarity. For a better use is recommended a twisted pair cable (22 AWG min).
Avoid placing instrument near devices powered in AC or Switching. Connect ground-tap of the instrument
to the local common earth (PE). For shielded cables, earth the shield at the power supply ground only.
Warning: impedance of the cables defines the possible maximum length for digital
communication. It's recommended using cable with a low impedance. The maximum
length of the point to point connection, with a load of 250 ohm and single twisted cable
22 AWG-207 pF/m it's about 1000 meters.
The maximum connection length for the analog signal only is limited by the loads
(connected devices and cable) present in the current loop.
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To obtain output signal of 4-20 mA, you have to determine the minimum supply voltage as a function
of the load relation: see below figure. From the following formula you can achieve the right minimum
value of supply voltage:
Vcc = 0.023xR + 12.5
The power supply source to assure a minimum current value of 24 mA.
Where: R = output load..
Warning: for the digital communication to function properly, a minimum 250Ω load
must be present in the loop.
Load (OHM)
Not Operative
Area
Digital Communication
and 4-20 mA
4-20 mA
Only
Power supply (V)
Fig. 4 - Power supply/load
Power
Supply
Intrinsic Safety Barrier
Indicator
Controller
or
Recorder
Fig. 5 - Transmitter wiring
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3.3.1 Point to point connection
Make connection as shown in Fig.6
Power
supply
Fig. 6 - Point to point connection
RL=250 OHM min.
Connection to the Master for digital communication is possible at points A-B or B-C.
3.3.2 Multidrop connection (Digital signal only)
Make connection as shown in Fig.7
Connection to the Master for digital communication is possible at points A-B or B-C. in the Fig. 7
Power
supply
Fig. 7 - Multidrop connection
Note: At maximum 15 transmitters could be connected in parallel on the same line.
Warning: pay attention that for a right working of the digital communication a minimum
load of 250 ohm is necessary.
Warning: When more transmitters are connected on the same line the current standing
on the resistor (250-ohm) is equal to 4mA x N of connected instruments
This could cause a high electric potential. Be sure power supply is sufficient.
3.4 Safety instructions
3.4.1General
Instruments of the LD256 series are Transmitters of relative pressure. They are devices with solid state
electronics whose operation is based on piezoresitive sensors. They measure pressures of liquids,
gas and vapors with nominal ranges from 22 mbar up to 400 bar and transmit an current output signal
4-20 mA proportional to the measured pressure. They can also be used to measure level in open
or closed tanks or for measures of flow measuring the differential pressure on a calibrated orifice.
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3.4.2 Premise (Intrinsically safety)
The series LD256 are used for measures of pressure, this series are manufactured only for the
employment in areas with presence of potentially explosive atmospheres. The transmitters object
of the present instructions are characterized by the following methods of protection:
Ex ia II C T6 with T amb -20 + +40°C
Ex ia II C T5 with T amb -20 + +55°C
Ex ia II C T4 with T amb -20 + +80°C*
The indications contained in the present safety instructions must be observed together with the
instructions brought in the operator manual.
* Note: for use with T amb.> 60°C please see the table "Electrical parameters related to Intrinsic
Safety" at par. 2.4.3.4
3.4.3 Installation
3.4.3.1 Fitness of the transmitter for the installation area
In case of use in areas with danger of explosion, it must be verified that the identified type of transmitter fits for the classification of the zone and for the presence of flammable substances in the plant.
The safety essential requisite against the risk of explosion in the classified areas are fixed from
the European Directives 94/9/CE of March 23 rd 1994 (as far as it concerns the apparatus) and
1999/92/CE of December 16 th 1999 (as far as it concerns the plant).
3.4.3.2 Intrinsically safety data definitions
II 1G
Ex ia
IIC
T6, T5, T4
Transmitter for surface plants with presence of gas or vapors, Group II,
category 1, fit for zone 0 and with redundancy for zone 1 and 2
Intrinsically Safe transmitter, category "ia"
Group IIC apparatus, fit for substances (gas) of group IIC
Temperature Class of the transmitter (maximum temperature)
Conformity mark to European Directives applicable to the apparatus
Conformity marking to 94/9/CE Directive and technical rules
CESI YY ATEX NNN
0722
T. amb
Ui, li, Pi, Ci, Li
Name of the laboratory that released the EC type-examination certificate;
YY=Year; NNN=certificate number
Identifying Number of the notified body (CESI) that assess the quality
system of the manufacturer
Ambient minimum and maximum temperature
Maximum Input parameters of the apparatus (related to intrinsic safety)
Note:
a) - the transmitters for the group IIC also fit for gas groups IIB and IIA;
b) - the transmitters with class of temperature T6 also fit for all the substances with higher class of
temperature (T5, T4, T3, T2, T1);
c) - the transmitters with class of temperature T5 also fit for all the substances with higher class of
temperature (T4, T3, T2, T1);
d) - the transmitters with class of temperature T4 also fit for all the substances with higher class of
temperature (T3, T2, T1);
e) - the choice of the associated apparatus must be made on the base of the maximum input
parameters of the transmitter.
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3.4.3.3 Additional Warnings for installation
For the correct installation refer to the chapter operator manual and to sketches brought there.
The process connection must be realized in such a way that guarantees the hold at the maximum
working pressure and temperature. Do not overcome the maximum pressure and temperatures
indicated in the technical data sheet of the selected model. When the device is connected to the
process it can be submitted to high pressures and temperatures. To avoid accidents subsequent to
sudden discharge of pressure and/or to contact with dangerous or flammable fluids it is necessary
to take the maximum attention when the device is taken off, heated or repaired, verifying that it is
isolated from the process and is not submitted to pressure and/or temperature.
R (Ohm)
1070
837
600
170
Exi
Exi +
HART®
Non
Exi
Exi
12
30
35
V supply (Vcc)
Operative area
3.4.3.4 Electrical connections (Intrinsically safety)
For the electrical connections please follow the instructions brought in the operator manuals taking
care that for the use in classified areas it is necessary to foresee the use of associated apparatuses (
e.g. safety barriers), certified according to the standard EN 50020, with output electrical characteristics
compatible with the maximum input parameters (brought on the plate) of the certified transmitter. The
evaluation of the system constituted by the associated apparatus, the transmitter and the cables of
connection must be done by experienced personnel only and must match the requisite of the standard EN 50039 relative to the intrinsically safe systems. For the correct installation it is necessary
to follow the safety instructions of the selected associated apparatus.
Electrical parameters related to Intrinsic Safety
Parameter
Maximum input voltage Ui
Maximum input current Ii
Maximum input power Pi
Maximum internal capacitance Ci
Maximum internal inductance Li
For T amb < 60°C
30 V
100 mA
0,75 W
10 nF
0H
For T amb < 80°C
25,2 V
100 mA
0,62 W
10 nF
0H
3.4.4 Control and Maintenance
The verifications and the maintenances of the transmitters must be done according to the criterions
of the standard EN60079-17.
3.4.5 Instrument Service
In case of malfunction or damage it is advised to contact Spirax Sarco service department.
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3.5 Pressure measurement
The transmitter LD256 may be used for pressure and level measure on open tank in the ranges
showed in the table on first paragraph of this manual and mounting. On Fig.9 and 9.1 it is shown
the simplest mounting, direct on piping.
Warning: the diaphragm seal must be always covered by the liquid.
Liquid
Vent
Pressure
Measurement
Vent
Gas
Fig. 9
Open tank level
Dash line for
closed tank
with day leg
Vent
Vent
25 mm
Fig. 9.1
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4.1Operations
4. Configuration
The transmitter shows the status and the measure on the dot matrix LCD (see fig.10). The span is
from -99999 to 999999.
The input signal to the transmitter can be related to the output signal in the following ways:
- Direct mode = 4÷20mA output
- Reverse mode = 20÷4mA output
The direct mode is obtained by setting the lower range point with the lowest value of the range (e.g.
0bar o 0m3/h) and by setting the upper range point with the highest value (e.g. 5bar o 1000m3/h).
The reverse mode is obtained by setting the lower range point with the highest value of the range
(e.g. 5bar o 1000m3/h) and by setting the upper range point with the lowest value (e.g. 0bar o 0m3/h).
To display the temperature values of the sensor (not in flow meters mode) and of the electronic
board push the following keys during transmitter operation:
 = sensor temperature (differential pressure);
 = electronic board temperature.
The unit of measure (°C) is defined in the entry TEMP UNIT in the keyboard menu (follows).
In the volumetric flowmeter the pressing of button display the differential pressure.
4.2. Display and Keyboard
Measure display (6 digits)
Bargraph / % span
Measuring unit
Menu entering
Choice Bargraph / % span
Sensor T display
Elect. board T display
LCD Display and keyboard
Fig. 10 - Display and keyboard
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4.3 Keyboard configuration
The electronic transmitters have some configuration functions available via keyboard and LCD
display, provided with the instruments themselves.
Press the [MENU] button to enter the password entering dialog; the default password is 0000.
Confirm by [OK] to enter the configuration menu.
The password is in 4 digits format and spans from 0000 to 9999. If you can’t remember or find the
password you set, please contact our service department.
When the display is in numerical entering mode, the cursor will blink. To move the cursor press the 
button; to raise the value of the digit press the  button. Confirm with [OK].
Use the  and  buttons to show the sequence of the available functions and press [OK] to confirm
the selected function. The display will allow to choose from the different functions described in the
table below. Press the [OK] button to confirm; use instead the [MENU] button to cancel the modifications and to go back to the standard display.
Function
Zero setting
Full span setting
Measuring unit
selection
16
Display
name
Use
Choice span
LRV
Measure linked to the
zero and to the 4mA
output. The measuring
unit is shown in the lower
right corner of the display
Between the sensor limits
URV
Measure linked to the full
span and to the 20mA
output. The measuring
unit is shown in the lower
right corner of the display
Between the sensor limits
PV UNIT
(disabled in
volumetric
flow meters
mode)
Measuring unit selection
from the available ones.
Press  or  to scroll.
Pressure:
bar, mbar, Pa, KPa, MPa,
mmH2O, mH2O, cmH2O,
Kg/cm2, mmHg, psi, Torr, inHg,
Atm, ftH2O, g/cm2, inH2O
Level:
m, in, cm, mm
Density
specific gravity, g/cm3,
kg/m3, g/l
3.887.5275.200
Keyboard Configuration
Function
Display
name
Use
Choice span
Configuration of
PV
CONFIG PV
Selecting of the display
mode associated with
primary variable.
1 - PRESS. = pressure
Transfer function
XFR FUNC
(disabled in
volumetric
flow meters
mode)
Selecting of current output
in linear or square root
mode.
LIN = linear
SQRT = volumetric flowmeter
Fluid density
GM
available in
volumetric
flow meters
mode)
Insert the fluid density in
Kg/m3 measure unit.
>0
[Kg/m3]
Fault
configuration
ALARM TYPE
Fault condition analog
output selection.
NONE = no action
21.5mA
3.85mA
LAST = last read value
Damping setting
DAMP VALUE
Insert the signal averaging
time constant.
0÷60s
OFFSET
The transmitter links the
actual reference input to
the zero display measure.
The transmitter will then
show 0 at display after the
confirmation by [OK].
-
SET LRV
At button pushing the
transmitter will
automatically link the
4mA output to the actual
reference input.
-
Zero re-setting
4mA output
automatic setting
(zero)
3.887.5275.200
2 - FLOW = flow meter
17
Keyboard Configuration
Function
20mA output
automatic setting
(span)
Automatic zero
elevation
Display
name
Use
SET URV
At button pushing the
transmitter will
automatically link the
20mA output to the actual
reference input.
At the button pushing the
transmitter performs the
zero elevation, in manner
SET ZEROEL
to put to zero the actual
measure. The elevation is
applied to the whole span.
Choice span
-
LOOP TEST
It is possible to fix the
analog output of the
transmitter to a required
mA value.
3,85÷21,5 mA
Analog output
calibration
CAL 4-20mA
The transmitter fixes the
output to 4mA and asks
by display to check the
value (OK? YES/NO).
Choose NO if the output
is incorrect and insert the
value read on an external
amperometer. Do it again
until necessary. The
same procedure for 20mA
follows.
-
Hart®
polling address
ADDRESS
Hart® polling address
modification.
0÷15
INFO
The polling address, the
lower sensor limit (LSL),
the upper sensor limit
(USL) and the firmware
revision are shown.
-
Analog output test
Transmitter
information
18
3.887.5275.200
Keyboard Configuration
Function
Display
name
Use
Choice span
Password setting
PASSWORD
Allows to insert a new
password
for the transmitter.
To be used with care.
0000÷9999
Expert
Command:
Manual zero
elevation
ZERO ELEV.
(disabled in
volumetric
flow meters
mode)
Manual zero
elevation insertion.
6 digits, including "–" sign
and decimal point
Expert
Command:
Gain setting
SG VALUE
Manual inverse gain
insertion (specific gravity)
0,1÷10
Factory setting
restore
RESTORE
Select and confirm using
buttons  and [OK].
-
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19
4.4 Remote operations via HART® protocol
The electronic transmitters LD256 are totally comply with the HART® protocol specification Revision
6.0, so they include remote process variable interrogation, parameter setting and diagnostics.
The device is a 4÷20mA 2-wire transmitter, with FSK communication.
It is possible to read via HART® the following variables:
 PV: transmitter main measure;
 SV: % of the span;
 TV: analog output;
In volumetric flowmeter configuration:
 TV: differential pressure
 QV: transmitter temperature.
Please refer to Fig. 12 for the Hart® modem connection on transmitter’s 4÷20 mA loop. In Fig. 11
the multidrop connection type is shown.
Hand-held
configuration
(HHT)
HART
server
USB, RS232, ...
HART
modem
15 HART transmitters
R = 250÷550 Ohm
Vcc = 24 Vdc
No 4÷20 mA loop
Fig. 11 - HART® connection multidrop
20
3.887.5275.200
Hand-held
configuration
(HHT)
HART
server
USB, RS232, ...
HART
modem
R = 250÷550 Ohm
Vcc = 24 Vdc
4÷20 mA loop
HART transmitters on polling address 0
Fig. 12 - HART® connection loop 4÷20 mA
4.4.1Maintenance
Transmitters do not require a maintenance on periodical basis.
Periodically check the general transmitter status, the possible presence of rust or damage on the
case or on the measuring diaphragm and the presence of clogging in the process connection.
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21
4.4.2Troubleshooting
Please refer to the following pages scheme for troubleshooting.
In any case contact our service department for help.
Condition
Potential source
Solution
Supply
Check the supply voltage to be
12Vdc<Vsupply<40Vdc.
Polarity
Check the transmitter connection polarity.
Electrical load
Check that the load is less than the maximum
allowed.
Process
Accurately verify the compatibility between the
process and the connection type.
Sensor drift
Apply zero input conditions to the transmitter
and use the OFFSET command.
EMC interference
Accurately verify the possible presence of
electromagnetic interference on the supply line.
Check the PE connection.
Wrong span limits
Use the LRV and URV commando (or SET LRV
and SET URV) to correct the output.
Uncalibrated analog
output
Use the LOOP TEST command to verify the
analog output calibration. If it is not correct,
use the CAL4-20mA command to calibrate the
output.
Uncorrect HART®
settings
Use the ADDRESS command to verify that the
polling address is set to 0.
Transmitter in fault
mode
Check if the output isn’t out of the allowed span
or check the presence of a failure (e1, e2, … on
display).
Wrong fault settings
Check the settings using the ALARM TYPE
command.
Unstable measure
Measuring disturbs
Set an input average using the DAMP VALUE
command (i.e. 10 seconds).
Impossible to
access the menu
Wrong / forgotten
password
Contact us for help.
The transmitter
doesn’t turn on
Measure is
uncorrect
Erratic analog
output
Analog output
<4mA o >20mA
22
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5. Spare parts
Together with the request of spare parts it is required to indicate Serial Number of the instrument
to control that the correct component will be delivered. Available spare parts are (with its own code
and mounting quantity in parenthesis).
Fig. 13 - Housing
Fig. 14 -Absolute and relative pressure
measuring element LD256
Housing (Fig. 13)
(1) Measuring element (see next figures);
(2) Plug for housing;
(3) Terminal board:
(4) Electronic module;
(5) Microcontroller;
(6) Name plate;
(7) Cable gland (2 pcs);
(8) Cover gasket;
(9) Forward cover with window;
(10)Display frontal protection;
(11) Rear cover.
Primary Element (Fig. 14)
(1) Measuring element.
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23
REPAIR
Please contact our nearest Branch Office or Agent or directly Spirax-Sarco S.r.l. - Ufficio resi
Via per Cinisello, 18 - 20834 Nova Milanese (MB) - Tel.: +39 0362 49 171 - Fax: +39 0362 49 17 307
LOSS OF GUARANTEE
Total or partial disregard of above instructions involves loss of any right to guarantee.
Spirax-Sarco S.r.l. - Via per Cinisello, 18 - 20834 Nova Milanese (MB) - Tel.: 0362 49 17.1 - Fax: 0362 49 17 307
3.887.5275.200 Issue 1 - 2014.07