Specifications

The D1000 module is initially calibrated at the factory and has a recom-
mended calibration interval of one year. Calibration constants are stored in
the EEPROM and may be trimmed using the Trim Span (TS) and Trim Zero
(TZ) commands. There are no pots to adjust. Calibration procedure is as
follows.
Voltage and current inputs: clear the output offset register using the Clear
Zero (CZ) command. Zero trims are not neccessary due to the built-in auto-
zero function. Apply a known calibrated voltage or current to the input of the
module. The calibrated stimulus should be adjusted to be near 90% of the
full scale output of the modules for best results. Obviously, the accuracy of
the calibrated voltage or current must be better than the rated accuracy of
the module, which in most cases is 0.02% of full scale. Use the Read Data
(RD) command to obtain an output reading. If the output corresponds to the
applied input, no calibration is necessary. If the output is in overload, check
the circuit connections or use a different input value to obtain an output within
the operating range of the module.
To trim the output, use the Trim Span (TS) command. The argument of the
TS command should correspond to the desired module output. After
performing the TS command, verify the trim with the RD command. For
example to trim a D1121 module:
1. Clear the output offset register.
Command: $1WE
Response: * (CZ is write protected)
Command: $1CZ
Response: *
2. Apply an input voltage near 90% of rated full scale. In this case we will use
a +900mV input voltage that is accurate to at least 0.02%. Obtain an output
reading.
Command: $1RD
Response: *+00900.30
In this case, the output of the module is off by 300µV. To trim:
Command: $1WE
Response: * (TS is write protected)
Command: $1TS+00900.00
Response: *
Chapter 9
Calibration