PT200MI instruction manual 5
3. OPERATION
3.1 GENERAL RULES
Do not install the PT200MI in direct sunshine, and avoid sudden temperature changes, vibration or wind.
The best environment is when the temperature is about 20 or 68 and the relative humidity is about ℃ ℉
50%.
Ground the PT200MI via the power cable to the rear terminal and ensure a good ground connection. Do
not ground directly to other equipment.
Analogue input/output signals are sensitive to electrical noise. Do not bind these cables together as it could
result in cross-talk interference. Please also keep them well away from AC power cables, and keep all
cables as short as possible.
If the local AC electrical supply fluctuates by more than ±10% an AC regulator must be used in order to
stabilize the power and reduce power spikes.
3.2 INPUT SENSITIVITY OF LOAD CELLS
The input sensitivity (A) of the load cells can be calculated from the following formula:
A = (Live weight of the scale)/(Number of load cells)/(Load cell capacity)*(Load cell mV/V at
capacity)*(Excitation voltage)*(1000 for microvolts)/(Scale resolution in divisions)
Alternatively
A = (Load cell output voltage at scale capacity - load cell output voltage at dead
load) × Step width / Scale capacity
PT200MI requires that “A” must be greater than or equal to 0.5μV/D.
3.3 CONNECTING THE LOAD CELL TO THE INDICATOR
The analogue output from the Load cell and the RS232/RS485 input/output signals are sensitive to electrical
noise. Do not bind these cables together as it could result in cross-talk interference. Please also keep them
well away from the AC power cables.
When the load cell has a 6 wire cable, connect Sense+ to Excitation+ and Sense – to Excitation -.
Load cell connections
Pin no. Signal
EXC+
EXC-
SIG+
SIG-
SHD
Excitation+ (Sense+)
Excitation - (Sense -)
Signal +
Signal -
Shield
SHDEXC-EXC+SIG-SIG+
PT200MI
EXC+
EXC-
SIG- SIG+
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