may be moved to the desired output. To return to the 4-20 mA mode, replace the JP3 jumper
on the “mA” pins and the JP2 jumper to the “4-20 mA” pins. Ensure that power to the
transmitter is off before attempting to change these settings.
The output signal is connected using a two-conductor shielded cable. The resistance of the
total cable length must be less than 250 Ω if the 4-20 mA current loop mode is selected. For
the voltage modes, the input impedance of the controller must be greater than 100 kΩ.
Ground the shield of the signal cable at an earth grounding point only to avoid noise conditions
created by ground loops. Although the positive signal lead can be shorted to ground without
causing damage, this condition should be avoided. Also, do not route the signal cable in
conduit containing other wiring to avoid unwanted noise pickup.
The linear outputs produce a signal based on the full scale response of the transmitter. As an
example, a Brasch Carbon Monoxide Transmitter has a full scale output of 200 PPM CO. For
the 4-20 mA output mode, 0 PPM CO would equal 4 mA while 200 PPM CO would equal 20
mA. Follow the instructions supplied with your controller to adjust the controller’s input for the
proper scaling of the signal. Consider a 0 mA or 0 VDC output as a fault condition. See figure
7 on page 27 for details.
Adjusting the Proportional Output
To adjust the output, set the jumper at JP2 on the bottom, right of the sensor board to the
desired unit – “Volts” or “mA”. Then set the jumper at JP3, just above JP2, to the desired
output signal – 2-10 V, 1-5 V, 0.2-1 V, or 4-20 mA. Be sure to follow the instructions on page
18 to ensure proper functionality of the proportional output.
Obtaining the Best Operation
Carbon Monoxide and/or Nitrogen Dioxide Transmitters
These transmitters are placed in areas to monitor for a rising concentration of the target gas.
No two installations will be exactly the same. The number of gas producing sources, air flow
patterns inside the room, the total room volume, and the exact location of the transmitter(s)
influence how effective each is in sensing the target gas concentration.
IOM02
Rev 1.0 – December 22, 2020
19
Note
Power to the transmitter must be turned off in order for any changes made to take effect.
