Specifications

D1500 Data Sheet D-4
The initial offset is +2.34mV. The D1521 has a useful input range of ±60mV.
After subtracting the offset the “input overhead” is -62.34mV and +57.66mV.
The expected 0 to +30mV output of the load cell easily falls within the
overhead range and no external trimming is necessary.
To Trim Zero:
Command: $1WE (TZ is write protected)
Response: *
Command: $1TZ+00000.00 (zero output)
Response: *
Now read the data output to verify the trim:
Command: $1RD (Read Data)
Response: *+00000.00
The load cell system has been trimmed to zero.
Example 2:
A strain gage bridge will be used to measure both compression and tensile
strains on a structural member. The bridge is attached to a D1521 module
and the ideal output from the bridge is ±30mV full scale.
Clear the Zero Trim:
Command: $1WE
Response: *
Command: $1CZ (Clear Zero)
Response: *
Measure the initial offset from the bridge:
Command: $1RD
Response: *-00043.21
In this case, the bridge exhibits a large initial offset of -43.21mV. Subtract this
value from the ± 60mV useful range of the D1521 to obtain and “input
overhead” value of -16.79mV to 103.21mV. In this case the -16.79mV
overhead is not large enough to cover the -30mV that may be obtained from
the bridge. The bridge must be trimmed externally to bring the offset to within
±30mV. It is not necessary to obtain an exact zero with the external trim.
After the external trim has been performed, check the offset:
Command: $1RD
Response: *-00022.22