I am searching for a device that will limit or clip output on a 4-20mA signal to 20mA. The information that was given to me from the instrument vendor is as follows:
General spec:
Signal isolator
24VDC supply
Isolated input and output (not loop powered)
Input range 4mA to 24mA (can be flexible here)
Output range maximum limit fixed to 20mA.
The output range should be configurable.
They may ask, driving impedance 500 ohm to 800 ohm would be nice
The idea is that no matter what the input mA level is, the output will never exceed 20mA.
Hi mikepowers,
Thank you for your inquiry. Please review datasheet of below options to make sure they work for your application before ordering:
Best options:
277-12422-ND
277-16828-ND
277-14807-ND
I am not strong with electronic devices. Will these devices clip or limit the output signal to 20mA, even if the input signal is higher than 20mA?
Hi mikepowers,
For the 277-12422-ND, the absolute max output current is 22mA, but this is a conservative spec. It will most likely be much closer to 20mA.
As another note regarding 277-12422-ND;
The max input current rating is 24mA, it is assumed exceeding this may damage the device.
-As there is an input resistance of 63 ohms, which would dissipate power:
Since these are configurable, it would also be important to make sure the configuration is set properly for your setup, and that both the input and output voltages, currents, and load requirements are within the specified ratings before installation to prevent damage or an unpredictable output.
Agreeing with David, the output would be closer to 20mA max, and most likely only approach 22mA if the input current would exceed the 20mA that it is calibrated for.
-Unfortunately it doesn’t look like this option would be able to ‘limit’ to 20mA max regardless of the input, as the datasheet does list 22mA max, but I don’t have one in-hand to physically test. An additional device or a different device all together may be of consideration.
