Klirrfaktor-Meßgerät KM-394B - Page 1
Forum section: electronics / testgear

author: MarkoAnte
author_rank: Regular Contributor
timestamp: October 08, 2013, 07:14:54 pm
content: Hi guys and gals,I'm new to the forums, but I have some knowhow of electronic - 3 year electrical engineering university (for what thats forth).So recently I whent and bought some old test equipment form a guy that had a audio-video repair shop and his business when under and he moved to Germany so I got some stuff for cheep and some for free. That brings me to thishttp://www.radiomuseum.org/r/nordmende_klirrfaktor_messgeraet_km.htmlhe gave it to me for free and told me that he didn't know if it was working or not.Now I would like to know if anybody has ever used this, or something like this and knows how to use it - as I'm not sure, if its broken or I just don't know how to use it. As a voltmeter it is ok, I have tested in on a variety of signals and it measures them ok but I don't know how to set up the Klirrfaktor measurement portion of the device. Some instructions and explanation would be nice.I also thought that the filter caps might be past it, so I tested some and they were ok (tested on HP4270).The photos of the control panel and rear panel (a pot is on the back and I don't know what it's for)http://shrani.si/f/3b/3K/1XpbH0ax/2013-10-08-210440.jpghttp://shrani.si/f/3d/5G/19S19GcW/2013-10-08-210455.jpgP.S. I have a poor understanding of German so that's a problem to

author: MarkoAnte
author_rank: Regular Contributor
timestamp: October 09, 2013, 03:49:30 pm
content: Anybody?

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 09, 2013, 04:43:01 pm
content: It's a distortion meter, I have never used one but I think that you have to feed it a sinus wave of one of the frequencies that you can select and then it can tell you the percentage of distortion, or in other words how much the wave is a pure sinus. I have no idea what the scale (0-100%) is based on though. It is used to measure amplifiers.

author: david77
author_rank: Frequent Contributor
timestamp: October 09, 2013, 05:51:44 pm
content: Exactly. It's a distortion meter used for alignment of tape recorders or general measurments concerning audio electronics. It shows "Klirrfaktor" in %, that's the same as THD%, total harmonic distortion. Also it has a AC mV meter function built in, in this unit capable of RMS measurments up to 2,5MHzIt puts out a relatively pure sinewave on the banana jacks under the meter. You select a frequency with the row of buttons, feed the output signal into your device under test and take a measurment e.g. using a regular scope probe connected to the BNC on the right.The selectable frequencies are according to what you would find in the service manuals for old reel to reel tape recorders built by German companies like Grundig, Telefunken or indeed Nordmende themselves. These frequencies were used to align the magnetic heads to give a flat frequency response of the device.I can not tell you how to align the meter properly, sorry. My guess is the Cal. button connects the input directly to the output of the sine generator and you adjust the meter to read 0% distortion, kind of like the relative function on a regular DVM.The pot on the back is a pre-adjustment for the calibration pot on the front.The output provides 1,55V (+6dBm) symmetrically or 0,775V (0dBm) asymetrically.

author: MarkoAnte
author_rank: Regular Contributor
timestamp: October 09, 2013, 07:58:29 pm
content: Ty david77 for the nice replay.Then the first problem I find is that it does not give out a sin wave, if I understood you right, if I look at the output off the banana jack and pres the 1K it should give me a 1Khz sinwave (and so on for the other frequencies too)

author: tekfan
author_rank: Frequent Contributor
timestamp: October 09, 2013, 09:07:18 pm
content: The setup for most of these old distortion analyzers is the same.This is how I think it works:1. Select CAL2. apply signal to BNC input3. select appropriate range and fine tune the meter pointer to full scale deflection with the CAL. 100% knob4. select the frequency of the applied signal with one of the square buttons5. adjust MIN. ABGL. for minimum meter reading6. switch range switch to a more sensitive setting and repeat step 5. (very sensitive on the low ranges)7. when the lowest reading is achieved the meter shows the distortion in %It looks like it really was used for adjusting tape recorders. The frequency ranges are fixed. If you want to look at the distortion of an amplifier you must applya signal to it as close to the selected frequency of the analyzer.The trimpot on the back looks like it has to do something with the signal before it reaches the front panel MIN. ABGL. potentiometer.Probably an adjustment so that the MIN. ABGL. control is somewhere near the center of its turning range when the meter is at its minimum reading.QuoteI've just started EE university in Ljubljana and it seems that we won't learn anything remotely useful for making electronic circuits.