0
\$\begingroup\$

When searching for voltage sensing transformers, I've come across this device on the internet: ZMPT107-1.

I far as I understood, this is a current transformer (it either uses a burden resistor or an transimpedance amplifier on the secondary), but I'm confused as the datasheet says it is used to sense voltage. How is this possible? Shouldn't it be fried when connected across higher voltages (most CTs have very low impedance)?

Also I'd like to know if there are small form voltage transformers for the sole purpose of sensing voltage waveforms of low frequency (i.e. 50 or 60 Hz), and if they exists, what are the part numbers.

\$\endgroup\$
1
  • 1
    \$\begingroup\$ The answer is on the second page of the linked data sheet. They use a limiting resistor R' in series. \$\endgroup\$
    – 11011100
    Commented Jan 24, 2022 at 16:38

1 Answer 1

Reset to default
3
\$\begingroup\$

the datasheet says it is used to sense voltage. How is this possible?

It is a current transformer and I think you may be confused by this diagram (I've added the red boxes): -

enter image description here

The red boxes surround the load resistance of the circuit you wish to measure the current of.

Shouldn't it be fried when connected across higher voltages (most CTs have very low impedance)?

Yes, it would fry if the current isn't limited - that's what the load resistor R' is trying to symbolize.

I'd like to know if there are small form voltage transformers for the sole purpose of sensing voltage waveforms of low frequency (i.e. 50 or 60 Hz), and if they exists, what are the part numbers.

Here's something you are going to get used to if you use this site; requests for product recommendations are off-topic.

\$\endgroup\$
2
  • \$\begingroup\$ Thanks Andy. So CTs can indeed be used to sense voltage if a limiting resistor is used? \$\endgroup\$
    – strange_bakery
    Commented Jan 24, 2022 at 16:57
  • 2
    \$\begingroup\$ That isn't what the article is saying. R' is the load resistor i.e. your motor or pump or transformer or whole house if you want. R' represents your load. But generally, a CT could do that but, it's problematic in that if you have a 1:1000 CT you probably want at least an amp flowing in the primary to get 1 mA on the secondary. If you are sensing 250 volts AC then the resistor would be 250 ohms and dissipate 250 watts so, not much of a useful solution. Of course if you went for 1 mA on the input, you'd be looking at trying to measure accurately 1 uA on the output. you do the math! \$\endgroup\$
    – Andy aka
    Commented Jan 24, 2022 at 17:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.