B873-012 and B875-012 Calibration
(Original Document)
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Required Tools
Calibration is recommended at 12 month intervals for operation at or below 405 C (1045 F), and at 6 month intervals between 405 and 605 C (1045 and 1405 F).
The following table indicates the tools required, to calibrate the B873-012 and B875-012 modules:
1.
A programmer
2.
A precision voltmeter
3.
An Analog DC Voltage/Current
4.
A 1/4 inch Phillips screwdriver
5.
A 1/8 inch standard screwdriver
6.
An adhesive for the trim pot adjusting screw (e.g. Locktight Glyptol)
Gain Adjustments Procedure
To achieve full accuracy of the module, allow it to warm up for one hour, with a valid input present at the channel to be used for the calibration. Without warm up, the accuracy of the data values will be +2 counts. The following table gives the steps for adjusting the gain on the B873-012 and B875-012 modules:
Step
Action
1
Remove trim pot access cover, located on the front panel.
2
Open module handle to expose connector(s) and terminal(s).
3
Unplug field wiring connector(s).
4
Set up Programmer to monitor the register for the channel used for calibration.
5
Connect the positive lead of the voltage source to the channel's input + terminal and the negative lead to the channel's input - terminal.
6
Set voltage source to output 9.99877 volts.
7
While monitoring the register, adjust the trimmer until the value toggles between 8191 and 8192 in binary mode.
8
Use an adhesive to secure the adjusting screw on the trimmer.
9
Disconnect input source.
10
Re-connect field wiring.
11
Close module handle.
12
Replace trim pot access cover.
Input Voltage to Output Data Conversion
The following is the input voltage to output data conversion chart.
Determining Data Value from Input Voltage
Calculation for determining data value from input voltage (refer to the figure above and the table below.
(input voltage + 10) X 409.6
Example: (refer to graph)
(6.88824 V + 10) x 409.6
16.88824 x 409.6 = 6917.4231
data value = 6917 (Rounded to the nearest whole number)
Data Value Reference Chart
The following is the data value reference chart for the B873-012 & B875-012 input modules.
Data Value
Input Voltage, Current, or Condition
0000
1. First three seconds after powerup
2. During failure recovery
3. Under range
0001
-9.99756 V
4096
1. 0.00000 V
2. No voltage at input terminal
8191
9.99756 V
8192
Over range