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Products => Test Equipment => Topic started by: calli on March 14, 2016, 07:05:54 pm

Title: Frequency on Uni-T 61E and more Questions...
Post by: calli on March 14, 2016, 07:05:54 pm

Hi,

I just bought a Uni-T 61E and it just came from Reichelt.de here in germany (yes :-).

I played a bit with it, removed the lcd transport foil... Oh another one under it... removed that... OK clean up that glue remain... NO it is a scratch. Ok, not very visible but... I can live with it.

More playing I thought I can try the Frequency metering. Put it on the wave form gen on my USB DSO (bitscope mini) and could measure a AC voltage, the switched with the YELLOW button to Hz. Nothing... Checked manual. tried again. Scoped, yes there is a signal.

No frequency or % on the Volt or mV. Then tried the seperate Hz/% on the main knob. Measures perfectly. WHAT? The manual states freq is possible and the labels on the knob also indicate this. But nothing.... What do I miss?

:-//

Cheers,
Carsten

Title: Re: Frequency on Uni-T 61E what?
Post by: Wytnucls on March 14, 2016, 08:34:43 pm

As the manual says, on AC Volt or AC Current selector position, the signal amplitude (RMS) must be above 30% of range to be able to show line frequency.

Title: Re: Frequency on Uni-T 61E what?
Post by: calli on March 14, 2016, 10:06:23 pm

Thanks @Wytnucls.

I must have skipped that part in the manual ;-)

And that Wave generator offsets only a small amplitude on a DC voltage. Bummer.

Cheers,
Carsten

Title: Re: Frequency on Uni-T 61E and more Questions...
Post by: calli on March 14, 2016, 10:26:37 pm

What should I expect from the PEAK button in AC Voltage? On a 9V AC wallwart it shows 10.4V (RMS right?) and PEAK Min -14V and PEAK Max +14V. Not what I would expect for practical measurements.

Or another  :palm: for me?

Carsten

Title: Re: Frequency on Uni-T 61E and more Questions...
Post by: Wytnucls on March 14, 2016, 11:03:11 pm

I don't know what the waveform is like, so 10.4V RMS is possible and peak shows you Vpp (peak to peak) or transients. 14V peak is about right for a sine signal. 14/10.4 will give you the crest factor. 1.414, for a sine wave.
You're unlikely to get accurate RMS values for a waveform with a crest factor above 3.

Title: Re: Frequency on Uni-T 61E and more Questions...
Post by: calli on March 15, 2016, 11:29:55 am

Ok, I took it for a Min/Max measurement.

One thing I noticed in the manual is the wiring for current measurement is a good way to blow the fuse: Attachment.

Carsten

Title: Re: Frequency on Uni-T 61E and more Questions...
Post by: Wytnucls on March 15, 2016, 12:34:33 pm

Well spotted. The Chinese manual for the 61E has the same mistake.
The manual for the 71 series, on the other hand, has it right with a resistor in series with the power supply.