17
MAIN UNIT
3
CONNECTIONS
3) Common mode voltage too high.
In many industrial applications, the signal from one mA transmitter may be
monitored by several instruments. These are always connected in series. If the
total series resistance of these instruments causes a voltage drop of more than
10V AND if it appears on the ground side of the logger, the common mode
range is exceeded. This will cause the input amplifier to saturate resulting in
inaccurate readings.
Solution 1 : move other instruments to positive side of channel.
Solution 2 : use isolation amplifiers.
4) Absurd value when measuring in current loop ( defect x-mitter? )
The logger shows an absurdly high value and the x-mitter seems to be defect.
This will be the result if the "Volt/Current" switch has been left in the Volt
position.
The x-mitter will try to output its current through the high impedance of a
voltage input instead of the 50
Ω
of the current shunt. It will consequently
output as much Voltage as it can, again making the input amplifiers saturate.
Solution : put the Dip-switch in the "Current" position.
