MOD420 Hansen 4-20 MA Output Module with Cable

OPTIONAL 4–20mA OUTPUT MODULE

The optional 4–20 mA output module (MOD420) provides a way to connect the Vari-Level to a computer or other device for refrigerant level monitoring or control purposes. Primary level monitoring and relay control is still maintained at the control unit. However, if total computer control is desired, use Hansen Techni-Level Transducer Probes having direct 4–20 mA output.

The MOD420 output module can be factory-installed and calibrated, or may be field upgraded. It is small enough to be easily added inside the standard control unit enclosure. See page 12 for example of MOD420 installed inside control unit. The output is electronically isolated to overcome interference with other transducers on the same power supply. Maximum load resistance is 1200 ohms. Required input voltage for MOD420 is 10–36V DC. The appropriate power supply unit (PSU) can be purchased from Hansen if needed.

If it is necessary to calibrate the MOD420, install an ammeter, digital readout or other device, as shown in diagram below. Enter simulation mode by depressing and holding the simulation mode button on the face of the control unit. Turn the level simulation adjustment screw until the digital readout displays 0%. While continuing to hold the simulation mode button, set the output current of the MOD420 to 4 mA using the Z (zero) calibration screw. Next, turn the level simulation adjustment screw until the digital readout displays 100%. Set the output current to 20 mA using the S (span) calibration screw. To confirm proper calibration, check for a 4 mA output at the 0% simulated level; a 12 mA output at the 50% simulated level; and a 20 mA output at the 100% simulated level. Adjust calibration if necessary. When the output is correct, return the simulated level to a percentage value between the control level and high level settings. This prevents alarms or cutouts from operating unexpectedly the next time the simulation mode is entered.

Notes:

1) Use an ammeter to adjust z (zero) and s (span) calibration and then remove.

2) Optional power supply (part no. Psu) available from hansen.

3) 250 ohm resistor not required for direct 4–20mA signal to computer.