Frequency-analog converter 2

[checonbill]

I have an application that I need to measure a 0-600vdc line with a frequency range from 2khz-3khz and need an analog output of either 0-10v or 4-20ma.Any ideas where to find this

 

[Skogsgurra]

Does the DC have a frequency?
Or do you mean that you want to measure a DC voltage with a BW of 2 to 3 kHz?
I'm afraid one needs that kind of detailed information to be able to help you further.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Comcokid]

What you are looking for is a voltage-to-frequency converter. Many circuit designs exist with typically a 0-10V input. You will need to divide down your 600V input (probably with a resistor divider) and possibly follow the divider with a buffer before feeding the V-to-F circuit you use.

 

[DRWeig]

Yes, please explain more or give us a diagram. Not enough info. Comcokid may be correct, but if your frequency is impressed on a variable voltage (0-600vdc?) then a simple divider might not do the trick with a fixed input.

Best to you,

Goober Dave

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[checonbill]

Skogsgurra Yes not enough information.I am looking to measure frequency on an induction melting power supply it is a variable frequency and runs at 575 vdc the frequency varies between 2khz and 3khz I would like a analog signal 0-10vdc so that I can monitor the frequency. Thanks for any help with this

 

[Skogsgurra]

Ok, it was a little bit like I thought. I think that your best option is to use a current transformer to measure the output current instead of the voltage. Then apply the current transformer output to a resistor to scale the voltage and then to a frequency to analog module like this one:

http://www.laurels.com/transmitter-frequency.htm

There are several options. It will take too long to describe them all here. But what is said above is essentially the gist of it.



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[DRWeig]

I agree, Gunnar. Simple and accurate.

Best to you,

Goober Dave

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[IRstuff]

It would certainly help to stop referring to it as Vdc, since it's actually a Vac.

TTFN
faq731-376

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[Skogsgurra]

My impression was that the OP wanted to measure the ripple on the DC link (need to measure a 0-600vdc line with a frequency range from 2khz-3khz). But that may also be wrong. In that case, checonbill (Electrical) needs help from someone that is electrical and not (Electrical)

If he were in Sweden, I could certainly have done the job for him. But that is highly unlikely.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[IRstuff]

Possibly, but then he said, "measure frequency on an induction melting power supply it is a variable frequency and runs at 575 vdc" which seems to say something else.


TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[Comcokid]

OK - I read his OP wrong. I though he wanted to measure voltage of a 600 line with a frequency output of 10V or 4-20ma.

 

[checonbill]

I need to measure the frequency of a DC line that is 575 volts. The power is controlled variably with an scr fired controller. Sorry for the confusion with this application

 

[Skogsgurra]

Back to DC again? Sorry, DC doesn't have a frequency.

WHAT is the application? WHAT do you want to measure?

We can guess, yes. But as long as you keep talking about DC, nothing seems right.



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[checonbill]

What we have is a scr firing a DC voltage I need to measure the frequency that the scr is firing the DC voltage

 

[Skogsgurra]

OK. I assume that there is a firing unit? Then, there are a couple (or more) transistors driving isolation transformers that are feeding the SCR gates.

Your best option, if this is the case, is to connect a frequency counter between the cathode of one of those transistors and the 12 V (or 15 V or 24 V or whatever) ground. The frequency counter then shows the frequency with which the thyristor is fired and that, with a high degree of probabability, is what you want to know.

My patience is running out. Please do not tell us once more that you want to measure the frequency of a DC voltage.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.