model 2704 controller installation and operation handbook - Soliton

2704 Controller Transducer Scaling
19.2. SHUNT CALIBRATION
Shunt calibration is so called since it refers to switching a calibration resistor across one arm
of the four wire measurement bridge in a strain gauge transducer. It also requires the use of a
Transducer Power Supply module wired as shown in Figure 2-13.
The strain gauge transducer is calibrated as follows:
1. Remove any load from the transducer to establish a zero reference.
2. Enter ‘Scale Low’ and ‘Scale High’ values which are normally set at 0% and 80% of the
span of the transducer.
3. Start the procedure using the low point calibration parameter ‘Start Pnt1 Cal’, or a digital
input wired to this parameter.
The controller will automatically perform the following sequence:
1. Disconnect the shunt resistor
2. Calculate the low point calibration value by continuously averaging two lots of 50
measurements of the input until stable readings are obtained
3. Connect the shunt resistor
4. Calculate the high point calibration value by averaging two lots of 50 measurements of
the input
Strain gauge
C
Controller under
Calibration
B
A
Transducer power supply
D
Figure 19-1: Strain Gauge Calibration
Installation and Operation Handbook. Part No HA026502 Issue 1.0 Apr-00 19-3