steverino pussycat (Customer) asked a question.
I have the acuAMP devices mentioned feeding into a BX-08AD-3 to generate a kW measurement. The Amps are within published accuracy, but the VACT transmitter is flakey. It pushes 0.34 mA when the power is off, even if I short the VAC input terminals.
When I pick up the VAC transmitter with no input on the VAC terminals, the Volts on my display wander as high as 25VAC. This is a bench rig for working out the math so there isn't anything nearby to cause noise issues.
While I'm "running" (applying power to a heater,) I can force an offset to make it read correctly, but I feel the flighty nature of the part and the huge error at zero may be an issue. The AAC part I've used many times, but this is my first try with the VAC.
Thank you for any input. No pun intended. 😆
Steve Jamison
New Jersey Industrial Controls, LLC
Dover NJ
Just in case there are questions answered by this image:
I deleted my previous post after seeing the picture.
If you are trying to measure power using a voltage and current input from two separate devices, I think you will always run into problems.
Load Controls LLC makes really good hardware built for doing what you want. If 3 phase power is your ultimate target for this project, even VFD output to a motor, their UPC works really well. We used them at a food processing plant where I used to work to actually measure temperature in a large mixer as a batch was cooled and it was accurate to within 0.1°C I was shocked to see it was monitoring the output of a Powerflex 40 VFD and questioned the design, but it was designed to deal with it and the only problems we ever had were related to the PLC input or the lookup table needing occasional adjustment to compensate for mechanical changes to the mixer (bearing or flutes being replaced).
https://www.loadcontrols.com/products/universal-power-cells/
They have other power monitors that might be more suitable for a single phase load.
https://www.loadcontrols.com/products/compact-power-sensors/
Many thanks, Okie from Muskogee. 😉
I was actually fascinated by the fact the kW readings were dead on despite the VACT being so flakey.
I'll get a transmitter from them and try it live. My circuit is single phase water cooled xenon arc with a very non-sinusoidal curve. I'm not certain when the AcuAmp current transmitter says "true RMS" it really means it. The circuit is heavily inductive and the power factor is about 0.92 to 1.00. My test rig was PF 1.000 as it was just a resistance heater.
The 120V requirement of the Load Controls rig for the power input and it doesn't appear to measure the actual Volts which makes the kW not even close to making a real power measurement.
The UPC has passthrough ports for current as well as voltage input terminals, so it uses both to compute power. I have not used their other compact TP-2 product I linked. I am confident from hands-on experience that the power measurement from the UPC is quite accurate, within their stated 0.5%.
Reading more about the compact unit, its voltage input is to be derived from the measured load wiring and it only accurate to within 2%.
If 120VAC is not available in your application, then the UPC may not be a good choice. And with that TP-2 device, if your load isn't 120VAC and you had to add a transformer, then it's no longer compact!