I recently purchased a 2 channel I2C current loop sensor (along with an Arduino Shield) in order to monitor an ultrasonic depth meter that uses a 4-20mA output. During my bench testing, I don’t seem to be able to measure or pass current through the loop sensor inputs. I have tested with both input 1 and input 2 with a current loop generator and get the same results. If I remove the sensor from the loop, I get accurate readings on my multimeter for the current being produced by the generator. As soon as I include the sensor in the loop, the actual current drops into the microamp range and is stable despite changes in the current generator settings. The reading produced in the Arduino seems to reflect this microamp signal. The first image shows values with the sensor in the loop. The second shows with the sensor removed. The power supply is 24v DC. The jumpers on the sensor are in their default positions according to documentation from the NCD.io website. Is this a defective sensor or, more likely, a problem with how I have it set up? Thanks in advance for your help!
The loop is powered by a 24V power supply. Its positive lead is wired into the signal generator AI+ terminal (24v loop input). The AIo (4-20ma signal) terminal is then wired to my multimeter positive lead. The multimeter neg lead is then connected to the IN1 (or IN2) terminal on the Receiver. The corresponding G terminal is then wired back to the negative lead on the 24V power supply. The receiver board is being powered through the I2C interface. Does that answer your question?
When the multimeter reads the correct loop amperage, I have the receiver disconnected and the negative multimeter lead connected to ground on the power supply.
I think it is no necessary the external power supply, because the 2-Channel 4-20 mA Current Loop Receiver 16-Bit ADS1115 I2C Mini Module has Onboard 16V Voltage Supply (Boosted from 5V), try connect only the multimeter, and the current generator in the current loop.
Ok. Thank you. I’m not sure I understand the documentation then. I see where the boosted 16V for powering the “current shunt monitoring chip” but it isn’t clear to me that I was supposed to interpret that as meaning a current loop supply. I’m sure I have damaged the board then. If someone from NCD is listening, it might help some of us (at least it would have helped me) to revise the description to state: “Provides 16V current loop supply” or “No external loop power required” in the bullet list somehow. It would have saved me some money for sure. Thanks for helping me understand the problem.
