Once we developed the RS232 to 4-20ma Tx, we thought we should compliment it with this device. It lets an AMX master (or any device with a RS232 port) receive information from a 4-20ma loop device. Usually, these devices are sensors: temperature, pressure, flow, etc. We can provide this device so that it provides the loop current value. This value is usually within +/- 0.005ma of the actual current; at worst it is +/-0.02ma. We could also provide a device that merely provides the raw value of the ADC conversion (a count from 0 to 65535). Then you can interpret this value in the receiver’s software. Once again it will be a simple serial string:
- 0.000 to 20.000<CR> for ma conversion
- 0 to 65535<0x0D> for raw data
Recently (Jan 2017), we enhanced the firmware to add some other features to help one of our clients. His problem was his sensor was noisy which caused our device to send out a steady stream of serial data of very minute (inconsequential) changes in the current. So, we enhanced the basic mode of operation and added two more modes. The enhancement allows one to set a +/- delta which the change in current must exceed to trigger a report. You can make this delta anywhere from +/- 0.001ma to +/-0.099ma. In the first of the new modes, the device only issues a report when it is polled. And, the other added mode, causes the device to periodically issue a report (once every 3 to 60 seconds), if a 0.001ma change has occurred since the last report. The serial commands are once again simple with positive and negative feedback and are described in more detail in the manual.
Click on the image above for a larger view. Click on this link for the manual for this device: 4-20ma to RS232 Rx Manual
- 4-20ma to RS232 Rx – $245.00 (Current or raw data reporting)
- Programming for Custom Reporting – Call Us