OPERATING AND
INSTRUCTION MANUAL
FOR
MODEL DRC-6
GENERAL INFORMATION
1.1
Introduction
This manual provides t h e necessary information t o i n s t a l l , o p e r a t e
and maintain t h e Model DRC-6 D i g i t a l Thermometer,
1.2
Description
The DRC-6 D i g i t a l Thermometer i s a completely s e l f - c o n t a i n e d
temperature i n d i c a t o r with a b u i l t - i n r e f e r e n c e j u n c t i o n t h a t
a u t o m a t i c a l l y d i s p l a y s t h e temperature o f an a t t a c h e d platinum
r e s i s t a n c e thermometer (PRT) t o a r e s o l u t i o n o f one t e n t h degree.
The standard u n i t provides n o n - i s o l a t e d p a r a l l e l and s e r i a l BCD
outputs.
1.3
Specifications
1.3.1
Electrical Specifications
F u l l S c a l e Range
399.9 K
Number of D i g i t s
4
Resolution
0.1 K
Repeatability
±0.1 K f o r 30 min. a t
c o n s t a n t temperature
Linearization
F u l l y d i g i t a l w i t h 31
segment approximation
Input Impedance
100 megohms
Warmup Time
Rated accuracy ±0.1 K w i t h i n
5 minutes a f t e r power i s
a p p l i e d ; r a t e d accuracy a f t e r
20 minutes
Input: Power
Dual-primary; 115V/230V ±10%
s e l e c t i o n by jumper; 50-60 Hz;
10 w a t t s
1.3.1
(CONTINUED)
Common-Mode Rejection
Ratio, DC t o 60 Hz
CMRR t o D i g i t a l Ground:
none
CMRR t o Power Ground:
140 db with 300V i s o l a t i o n
Normal-Mode Noise Rejection
45 db a t 50 t o 60 Hz with
standard s e t t l i n g time
S e t t l i n g Time
2 seconds t o w i t h i n 0.1 K
after a f u l l - s c a l e step input
Reading Rates
I n t e r n a l Control Mode
From ½/sec t o 60 p e r / s e c
programmable by e x t e r n a l
resistor
External Control Mode
0 t o 60 readings/second
Maximum Normal Mode S i g n a l
135 mVRms
Sens o r E x c i t a t i o n
2mA
Sensor Input
4 wire
BCD Outputs
Parallel and s e r i a l ,
I .C. compatible
Display
0.6" high numerals, glow
d i s c h a r g e t y p e with
p o l a r i z e d view
screen
1.3.2
Mechanical S p e c i f i c a t i o n s
Dimensions
1 3 . 2 cm (5.2") wide x 6.4 cm (2.5")
high x 16.5 em (6.5") deep
Weight
1.8 Kg ( 4 pounds)
11.3.3
Operating Environment
Temperature
°0 t o 45°C
Relative Humidity
0 t o 75%, non-condensing.
Humidity-sealed boards
a v a i l a b l e f o r 90% RH
1.3.4
Temperature S p e c i f i c a t i o n s
Sensor Type
Platinum
100 ohms a t
273.16 K (0°C)
Sensor Mode1
PT-101, 102, or 103
Useful Range
4.0-400.0 K
Conformity Range
50.0-400.0
L i n e a r i z a t i o n Conformity*
0.2 K
Maximum D i g i t i z i n g Error
(8 h r s . a t 25°C)
0.1 K ±0.03% R
Maximum D i g i t i z i n g E r r o r
(90 days at 15-35 C)
0.2 K ±0.06% R
*To D I N 43740
1 .3.5
= 0.003850 ohms p e r ohm p e r
K
°C
Reference J u n c t i o n E r r o r
The s i g n a l c o n d i t i o n e r error for 10-40°C ambient i s less than
±0.08 K ±0.05% of reading i n a 24 hour p e r i o d .
RECEIVING I W D INSTALLATION
2.11
Unpacking and Inspection
Your Model DRC-6 D i g i t a l Thermometer has been c a r e f u l l y i n s p e c t e d
and t e s t e d b e f o r e shipment. Unpack t h e meter and perform a v i s u a l
inspection t o a s s u r e t h a t no damage has occurred d u r i n g shipment
o r handling. These meters are f a c t o r y s e a l e d u n i t s . The only
c o n t r o l s t h a t may r e q u i r e p e r i o d i c adjustment a r e a c c e s s i b l e through
t h e rear panel. Because e x t e n s i v e damage could r e s u l t from a t t e m p t s
t o measure c i r c u i t parameters o r t o trouble-shoot t h e meter by
non-factory p e r s o n n e l , t h e warranty i s a u t o m a t i c a l l y voided i f t h e
u n i t has been removed from i t s c a s e .
2.2
Installation-Mechanical
The f i g u r e below i l l u s t r a t e s t h e r e q u i r e d panel cut-out t o accept
t h e Model DRC-6 allowing t h e clamping b r a c k e t s t o g r i p t h e f r o n t panel
bezel t o t h e rack panel.
OPERATING INSTRUCTIONS
3. P
Wiring
A l l w i r i n g t o t h e Model DRC-6 i s accomplished from t h e rear of
t h e u n i t ( s e e drawing A-052-001).
Power w i r i n g i s t o a b a r r i e r s t r i p and t h e PRT w i r i n g t o
connecting t e r m i n a l l u g s . A l l c o n t r o l s and d i g i t a l connections
are v i a an edge c a r d connector.
NOTE:
3.1.1
To enable continuous r e a d i n g s , jumper 91-M t o 91-10.
Power Wiring
The s t a n d a r d u n i t o p e r a t e s from a 115V 2105, 50 t o 400 Hz power
s o u r c e , Operation from 23OV i s a v a i l a b l e as an o p t i o n and i s
accomplished v i a i n t e r n a l jumper connections.
The u n i t should be connected t o t h e power source with a t h r e e wire
c a b l e terminated a& t h e b a r r i e r s t r i p . The t h i r d wire provides
safe grounding of t h e case and should b e a t t a c h e d t o e a r t h ground
a t t h e power source.
3.1.2
EXTERNAL CONTROL WIRING
The f o l l o w i n g is a l i s t of t h e d i g i t a l input/output connections
f o r the Model DRC-6.
PIN
FUNCTION
PIN
FUNCTION
1°
1
4.0°
A
0.
2
8.0°
B
0.2°
3
10.0°
C
0.4°
4
20. 0°
D
0.8°
5
40.0"
E
1.0°
6
80.0°
F
2.0"
7
DATA READY ENABLE
H
DATA READY
8
TRANSFER
J
READY
9
100.0°
K
200. 0°
10
HOLD
L
S E R I A L BCD OUTPUT
11
SPARE
M
DIGITAL GND
12
NEGATIVE POLARITY
N
READ RATE
13
P O S I T I V E POLARITY
P
ERROR OR NEGATIVE POLARITY
14
ERROR (NEG TRUE)
R
RELAY DRIVE
15
RELAY CONTACT OUT
S
RELAY CONTACT OUT
3.1.3
Platinum Resistance Thermometer Wiring
The PRT i n p u t wires are a t t a c h e d d i r e c t l y t o t h e DRC-6 v i a terminal
lugs as i l l u s t r a t e d i n f i g u r e below. An o p t i o n a l 2-lead
c o n f i g u r a t i o n option i s provided by s h o r t i n g H i t o Lo and L 1 t o
L2 and connecting PRT between H i and L2.
3.2
External Control S i g n a l s
The following paragraphs d e s c r i b e t h e c o n t r o l s i g n a l s and t h e i r
functions. A l l s i g n a l s are a v a i l a b l e at t h e rear o f t h e u n i t . A l l
input/output l e v e l s are compatible with DTL and TTL l o g i c .
Input Signal Requirements :
False:
0 t o +.5V, s i n k 1.6ma
True:
+2.4 t o +5.5V, source .1ma
3.2
(CONTINUED)
Output S i g n a l S p e c i f i c a t i o n s :
False:
0 t o +.5V, s i n k 3.2ma
True:
+ 2 . 4 t o +5.5V, source .2ma
3.2.1
DATA READY (OUT)
The DATA READY s i g n a l goes t r u e (high) upon completion of a
measurement, and remains t r u e u n t i l t h e n e x t measurement i s s t a r t e d .
During t h i s time, t h e BCD o u t p u t s c o n s t i t u t e a v a l i d reading a v a i l a b l e
f o r use by an e x t e r n a l device. t h e DATA READY s i g n a l normally remains
t r u e f o r a t least 6 ms, and may be h e l d t r u e i n d e f i n i t e l y by keeping
t h e HOLD i n p u t t r u e .
3.2.2
HOLD ( I N )
Measurements may be e x t e r n a l l y c o n t r o l l e d a s d e s i r e d by use o f t h e
While t h e HOLD input is maintained false (low) ,
measurements occur a t t h e externally-programmed r e a d i n g r a t e (0.5 t o
60 p e r second). While it i s t r u e , t h e l a s t measurement i s h e l d i n
memory. An i n t e r n a l s t o r a g e element allows c o n t r o l by p u l s e s OF
transitions.
HOLD input.
3.2.3
READ RATE ( I N )
This i n p u t provides a means f o r a d j u s t i n g t h e reading rate from
approximately 0.5 p e r second t o 60 p e r second by eonneetion of a
r e s i s t o r between p i n N (READ RATE) and p i n M (GND),
Leaving t h e
READ RATE i n p u t open r e s u l t s i n a r e a d i n g rate of 0 . 5 / s e c o r
less, while a s h o r t r e s u l t s i n a 60/sec r a t e .
An approximate v a l u e o f programming r e s i s t o r f o r i n t e r m e d i a t e reading
rates may be determined from t h e formula:
5000
R = __
Kilohms
N-0.5
Where N i s t h e d e s i r e d readings p e r second.
The HOED i n p u t must be grounded f o r t h e reading rate t o be enabled.
3.2.4
BCD Outputs
The d i g i t a l o u t p u t s c o n s i s t o f t h e p a r a l l e l BCD e q u i v a l e n t of t h e
displayed temperature i n c l u d i n g magnitude, p o s i t i v e o r n e g a t i v e
p o l a r i t y , ERROR (low f o r e i t h e r overrange o r open i n p u t ) and an
output r e p r e s e n t i n g t h e l o g i c combination of ERROR or NEGATIVE
POLARITY.
In a d d i t i o n , a serial BCD output i s provided, I f i s o l a t e d p a r a l l e l
BCD o u t p u t s a r e d e s i r e d , t h e s e r i a l BCD output may be a p p l i e d t o a
s e p a r a t e package c o n t a i n i n g i s o l a t i n g transformers. The SERIAL
BCD OUTPUT may be accumulated and t r a n s f e r r e d t o s t o r a g e elements
by means of a TRANSFER p u l s e which also generates t h e r e s e t t o
p r e p a r e t h e BCD accumulator f o r t h e n e x t reading. The POSITIVE
POLARITY and NEGATIVE POLARITY o u t p u t s are timed t o be accepted
with t h e BCD d a t a .
3 . 2 .5
Relay Output (Optional)
A form A r e l a y c o n t a c t and d r i v e r a r e provided which may be a c t u a t e d
by any of t h e d i g i t a l BCD o u t p u t s . S e l e c t i o n i s achieved by
jumpering on t h e rear connector from Fin R t o t h e s e l e c t e d BCD
output. The r e l a y provides am i s o l a t e d c o n t a c t c l o s u r e on p i n s
15 and S.
THEORY OF OPERATION
The Model DRC-6 D i g i t a l Thermometer with i n t e r n a l r e f e r e n c e j u n c t i o n
a c c e p t s t h e r e s i s t a n c e output o f a platinum r e s i s t a n c e thermometer
(PRT) and provides a d i g i t a l d i s p l a y of t h e e q u i v a l e n t temperature.
Since t h e r e s i s t a n c e generated by a PRT is a n o n - l i n e a r f u n c t i o n o f
temperature, t h e a n a l o g - t o - d i g i t a l c o n v e r t e r c i r c u i t i n t h e Model DRC-6
i s made n o n - l i n e a r t o match t h e PRT curve. The curve i s approximated
by 31 s t r a i g h t l i n e segments t o reduce t h e conformity e r r o r t o less
t h a n t h e s t a n d a r d PRT e r r o r ,
A d i g i t a l l i n e a r i z a t i o n technique ( s e e f i g u r e 4.1) is used i n c o r p o r a t i n g
a Binary-Frequency-Generator (BFG) c o n t r o l l e d by a Read-Only-Memory (ROM),
The output o f t h e BFG s e r v e s as t h e clock s o u r c e f o r t h e modified
a n a l o g - t o - d i g i t a l converter. The 6 b i t b i n a r y coded d i g i t a l i n p u t t o
t h e BFG i s d e r i v e d from s i x o f t h e e i g h t p a r a l l e l o u t p u t s o f t h e ROM.
The remaining two b i t s are used t o s e l e c t one o f t h r e e a v a i l a b l e segment
l e n g t h s f o r a p a r t i c u l a r PRT type.
The f i v e b i t segment counter i s advanced at i n t e r v a l s o f t e n t h s of degrees
determined by t h e ROM and derived from t h e d i s p l a y counter. Each segment
i s r e p r e s e n t e d by one 8 b i t word i n t h e ROM. Segments corresponding t o
temperatures occur i n d i f f e r e n t s e c t i o n s o f t h e ROM and a r e s e l e c t e d
by a p o l a r i t y i n d i c a t i n g l o g i c l e v e l .
An i n t e r n a l r e f e r e n c e j u n c t i o n provides t h e i n t e r f a c e between t h e PRT
r e s i s t a n c e and i n p u t a m p l i f i e r . The i n p u t c i r c u i t i s a f i x e d gain
chopper a m p l i f i e r t o ensure d r i f t f r e e o p e r a t i o n with time and
temperature. There i s a t h r e e p o l e 5 H z f i l t e r f o r high n o i s e
r e j ect ion .
The s i g n a l c o n d i t i o n e r f o r t h e PRT is a m u l t i - c u r r e n t source ( s e e f i g u r e 3 . 1
on page 8 ) which provides 2 mA (I1) f o r t h e PRT and a second 2 mA
source (I2)f o r a balanced b r i d g e c o n f i g u r a t i o n . An a m p l i f i e r compensates
f o r any lead r e s i s t a n c e i n l e a d #4 o r any change with temperature o f
l e a d r e s i s t a n c e up t o a maximum lead r e s i s t a n c e of 100 ohms. The
output of t h e s i g n a l c o n d i t i o n e r is a v o l t a g e which i s d i r e c t l y
p r o p o r t i o n a l t o t h e s e n s o r r e s i s t a n c e and hence i t s temperature. Changes
i n lead #l r e s i s t a n c e are not seen by t h e i n p u t a m p l i f i e r and cause no
e r r o r . Leads #2 and # 3 do n o t c a r r y c u r r e n t and do not cause any e r r o r
due t o l e a d r e s i s t a n c e v a r i a t i o n .
FIGURE 4.1
BLOCK DIAGRAM OF MODEL DRC-6
CALIBRATION PROCEDURE
5.1
EQUIPMENT REQUIRED
1.
A v a r i a b l e r e s i s t a n c e source o f 0 t o 1000 ohms with
r e s o l u t i o n o f 0.01 ohms and accuracy o f 0.01%.
2.
Test c a b l e s a s i n d i c a t e d i n f i g u r e 5.1.
3.
An ice bath with b e t t e r than 0 . 2 degree s t a b i l i t y .
5.2
Procedure
5.2
INITIAL CALIBRATION
1.
Connect t e s t c a b l e s between v a r i a b l e r e s i s t a n c e source
and Model DRC-6 t e r m i n a l s l a b e l e d H I and L2. Connect
a jumper between t e r m i n a l s l a b e l e d H I and LO and a
second jumper between t e r m i n a l s L1 and L 2 .
2.
S e t span a d j u s t and zero a d j u s t potentiometers (see
figure 5 . 2 ) t o center scale.
3.
Adjust v a r i a b l e r e s i s t a n c e source t o read 0.00 ohms,
4. Observe and record reading.
5.
Adjust r e s i s t a n c e source t o 141.10 ohms and n o t e and
record readout.
6,
I f t h e d i f f e r e n c e between readings observed i n s t e p 4
and 5 i s n o t 380.0 K , a d j u s t SPAN a d j u s t potentiometer
u n t i l t h e readout d i f f e r e n c e i s 380.0 K when d i a l i n g
i n t h e r e s i s t a n c e provided i n s t e p 4 and 5 .
7.
Adjust r e s i s t a n c e source f o r 0.00 ohms and observe a
r e a d i n g of 10.6 K . I f u n i t does n o t d i s p l a y 10.6 K,
then a d j u s t ZERO a d j u s t potentiometer u n t i l a reading
o f 10.6 K appears,
8.
Adjust r e s i s t a n c e source t o 141.10 ohms t o check t h a t
u n i t i s d i s p l a y i n g 390.6 K.
5.3
CALIBRATION PROCEDURE WITH A PRT
AND A KNOWN TEMPERATURE
1.
Connect a PRT s e n s o r as i l l u s t r a t e d i n f i g u r e 5 . 1 .
2.
S t a b i l i z e PRT i n a 273 K bath ( i c e bath) and a d j u s t
ZERO a d j u s t potentiometer f o r 273.2 K i n d i c a t i o n .
3.
S t a b i l i z e PRT t o a known temperature (such as LN2)
and a d j u s t SPAN a d j u s t potentiometer f o r required
temperature i n d i c a t i o n .
Note:
This adjustment should b e minor and performed
a f t e r i n i t i a l c a l i b r a t i o n i n Section 5 . 2
above. E r r o r s should not be g r e a t e r than
accuracy of temperature source, PRT s e n s o r
and ±0.1 K ±0.1% of reading.