APPLICATION NOTE
On-line Measurement of Specific Gravity for Accurate and Efficient
Quality Control
Industry: Food & Beverage
Product: Liquid Density Meter
Introduction
In the food industry, the control of concentrations on the
production line is critical to product quality, determining, among
other things, how good the food tastes. One such procedure for
doing this involves taking a sample from the production process
and measuring its specific gravity (density) with a hydrometer.
This is a time-consuming manual procedure, however, and
results may vary depending on the operator.
This application note introduces a lactic acid beverage blending
process to show how on-line measurement with the DM8
vibration liquid density meter can improve the efficiency of
product quality control.
Expected Benefits
– Raises the accuracy and efficiency of quality control on food
and beverage production lines
– Improves the efficiency of preventive monitoring
– Reduces operating costs
Process Overview
In the blending (dilution) process at a lactic acid beverage plant, the product concentration was controlled by manually measuring the
liquid density. The plant now uses an on-line measurement process based on the DM8 liquid density meter, as shown in the following
figure. This achieves high accuracy in concentration control as well as increased efficiency in loss control and preventive monitoring.
P
To Filling Machine
Blender
Output Signal
0 - 1 V DC
4 - 20 mA DC
Density Detector
Density Converter
Surge Tank
Pump
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AN 10T01K01-03E
All Rights Reserved, Copyright © 2007, Yokogawa Electric Corporation
APPLICATION NOTE
Solution Details
Measurement System
Utilities
Sanitary use detector:
VD6DS-S3*B
Converter:
DM8C-A*C
Dedicated cable:
DM8W-L*A
DM8C converter/VD6DS detector:
Power supply (to converter): 90 to 132/180 to 264 V AC, 50/60 Hz
Power consumption:
Sampling system:
20 VA
The VD6SM sampling unit is not designed for sanitary use. For
a sanitary use sampling unit, contact Yokogawa.
Field Data
Results
Process conditions
Pressure:
150 kPa
Temperature:
4 to 6 °C
1.0740
On-line measurement using the DM8 vibration liquid density
meter enables the automation of various controls, thereby
improving efficiency.
R's Variation Per Day
Vibration Liquid Density Meter vs. Hydrometer
R = Hydrometer measure value – Density meter reading (×1/10–4)
+10
Density Meter Reading
+5
0
-5
-10
Jan. 21 Jan. 22 Jan. 23 Jan.26 Jan.27 Jan.28 Jan. 29
Jan. 30
R=-0.68x10
σ=1.442x10-4
-4
To adjust the density meter reading to the hydrometer measured value,
a specific gravity value of 0.00006 should be moved in parallel.
1.0720
1.0730
1.0740
Hydrometer Measured Value (15 °C, After Air Removal)
http://www.yokogawa.com/an/index.htm
AN 10T01K01-03E
All Rights Reserved, Copyright © 2007, Yokogawa Electric Corporation
3rd Ed: Jan.2011 (YK)