Designing A Multimeter (PW-June-1965), by K. Berry, presented by Peter Vis

[Chan Tran]

Ah, classic example of German engineering (and design) . Active multimeter with 2.5% accuracy and 10MOhm impedance. Why not trust a company that is also famous for their light meters when it comes to a multimeter for camera repair .

That particular model of the Gossen Metrawatt is very expensive to get.

 

[lumoStoria]

Yours analog meter isn't a simple meter (passive like Andrea said) as I believe it has high impedance OP amp input stage to give it as high input impedance as a typical digital multimeter. It also has a liner resistance scale.

Yes, I mentioned in post #2 above that the PM-2505 is an active multimeter. My point is that you should only use a passive multimeter if it has at least 10-20kOhm/V input impedance (like the one @4season presented) for low-current circuitry like the one in SLRs. If in doubt, it is always better to use an active multimeter. I think even the cheaper ones have a voltage-independent impedance of 10MOhm (like the PM-2505 has). Often, you can get these multimeters from reputable manufacturers like Gossen, Philips, or even Fluke for quite cheap on the used market. Most people have inherited the devices and have no interest in them (or not even know exactly what it is). As long as the batteries have not leaked (similar problem as with cameras) they usually still work.

 

[lumoStoria]

That particular model of the Gossen Metrawatt is very expensive to get.

Andreas only buys the good stuff .

I just checked for how much they sell and was like 'WTF?'.

 

[Andreas Thaler]

That particular model of the Gossen Metrawatt is very expensive to get.

This one is not exactly cheap either

I figured it’s worth investing in good equipment that will hopefully last a long time.

This multimeter really comes in handy when dealing with currents in the microamp range, which my EUR 25 multimeter can’t measure.

 

[Andreas Thaler]

Andreas only buys the good stuff .

I just checked for how much they sell and was like 'WTF?'.

You can spend as much money as you want on devices—there’s no limit. Compared to high-quality oscilloscopes, lab power supplies, and soldering stations, multimeters are actually quite affordable; you could easily spend thousands of euros on those. It depends on what you’re doing. Fortunately, I don’t need that for my projects.

 

[lumoStoria]

You can spend as much money as you want on them—there’s no limit. Compared to high-quality oscilloscopes, lab power supplies, and soldering stations, multimeters are actually quite affordable; you could easily spend thousands of euros on those. It depends on what you’re doing. Fortunately, I don’t need that for my projects.

You're right, these devices can be very expensive. However, for a hobbyist doing the "usual" electronics stuff there is a point on the curve of dimishing marginal utility where spending more is no longer justified by the extra quality/functionality of the device. Of course, scientific research or product development is a different topic.

I usually try to buy from the "middle" segment because this seems to be the sweet spot regarding price, functionality, durability, and accuracy. Also I sometimes overshoot; I know that I not really need a multimeter like my Agilent 34401A with 0.004% accuracy but sometimes you just have to treat yourself . Fortunately, I didn't have to buy any of this stuff for camera repair but had everything already available. Otherwise, I would have reconsidered entering this hobby.

 

[Chan Tran]

You're right, these devices can be very expensive. However, for a hobbyist doing the "usual" electronics stuff there is a point on the curve of dimishing marginal utility where spending more is no longer justified by the extra quality/functionality of the device. Of course, scientific research or product development is a different topic.

I usually try to buy from the "middle" segment because this seems to be the sweet spot regarding price, functionality, durability, and accuracy. Also I sometimes overshoot; I know that I not really need a multimeter like my Agilent 34401A with 0.004% accuracy but sometimes you just have to treat yourself . Fortunately, I didn't have to buy any of this stuff for camera repair but had everything already available. Otherwise, I would have reconsidered entering this hobby.

In context the considered overkill Agilent 34401a isn't that much more than the Metrawatt and the accuracy is 100 times more.

 

[lumoStoria]

In context the considered overkill Agilent 34401a isn't that much more than the Metrawatt and the accuracy is 100 times more.

Sure but the footprint of the Agilent is huge on the bench (about 38cm deep plus power cable), has a noisy fan, isn't that straightforward to use, and if the VFD display breaks you're screwed. Currently, I mainly use it for calibrating and adjusting other multimeters. Don't see any application in camera repair my Brymen BM257s couldn't do for much cheaper.

 

[chuckroast]

Only this particular type, which is no longer being made or used. More modern solutions of course also involve Ohm's law at some point.


Then again, back in those days, you needed that voltage range!

You still do in some settings, just not in camera repair. Among them include, broadcast transmitters, linear amplifiers for amateur radio, and maritime radars.

I have worked on all the above at one point or another, and analog meters still very much have a place. The visual of the needle swing helps when trying to peak or null a reading, for instance, something more common that many people believe. "Modern" meters tend to use digital displays which can be misleading if you don't understand the limits of their resolution. There is also a tendency to believe that digital is more "accurate" than analog and that's not inherently so - it depends on how the meters in question were designed and calibrated.

In any case, I will never part with my Simpson 160 and 260 multimeters, even though I have ample digital alternatives at my disposal.