Zero and Span Adjustment
Each channel is individually adjustable for zero and span. Adjustment is via front panel potentiometers
marked Z (zero) and S (span). The procedure for zero and span adjustment is given below.
1. Attach a milliammeter and power supply to the output terminals as shown below.
2. Attach the slidewire and place it in its zero position. Adjust the zero potentiometer until the
milliammeter shows a reading of 4mA (or 4.0 etc.). If a 4mA output is not achievable then
adjustment to the slidewire linkage position may be required. The RM3 requires that at the 4mA
end the mechanical position of the wiper is at, or very close to (within 20% of full travel), zero.
3. Move the slidewire wiper to its full scale position. Adjust the span potentiometer until the
milliammeter shows a reading of 20mA (or 20.00 etc.).
Note: If it is not possible to input the exact value for 20mA then input a value corresponding to an
output of as close to 20mA as you can and adjust the span potentiometer until the required mA
output for this input is reached. The span adjustment allows the 20mA output to be placed
anywhere in the range from 60% to 100% of the slidewire full scale travel.
Typical Zero and Span adjustment setup
Page 5 of 7
RM3SWMAN-1.1-0
+
+
-
-
Slidewire
Milliammeter
24V
Loop Supply
4
5
4
5
2
3
5
4
S
Z
Z
O/P
S
Z
S
S
Z
3
2
1
3
1
1
1
2
2
3
4
5
RM3
SERIES
AMALGAMATED INSTRUMENT CO
O/P
O/P
O/P
