Now that's 1 out of 4 instruments that I want to start with. In one of Dave's video blogs he recommended the HP/Agilent 3478A bench multimeter. I've been searching around in ebay and it seems like I can get a hold of one for <$150 which is good and all. Dave seems to be very confident with it in the blog, but one thing that worries me is that the calibration dial is exposed in the front. Do I have to cross my fingers that the previous owner haven't tweaked that (I called a local calibration company and they want $137 to calibrate the specific model)? Is there anything else that enyone would recomend for a budget bench multimeter?
I like that one too, the only issues are a non-backlit LCD display (may be hard to read depending on your lighting), and no diode/continuity test. I think $150 is a bit on the high side, around $100 should be possible. Though if you can get some sort of guarantee, that would be worth extra. One alternative is the HP 3468A, it's almost identical, but lacks the GPIB interface (may or may not be important for you), and I think the 3478A has one extra lower ohms range. It is usually significantly cheaper. Depending on the required feature set (accuracy, resolution, auto ranging, 4-wire, current), there are various models from Fluke and Keithley that might work. For example:
- Fluke 8600A: 4.5 digit LED , auto-ranging, no 4-wire ohms
- Fluke 8800A: 5.5 digit LED, auto-ranging, 4-wire ohms, no current
- Fluke 8810A: like the 8800A, slightly newer, but AC and ohms were optional
- Keithley 175(A): 4.5 digit LCD, auto-ranging- 4-wire ohms, the -A version adds backlight, GPIB and battery were optional
- Keithley 192: 5.5 digit (6.5 digits on some ranges) LED, auto-ranging, 4-wire ohms, no current, AC volts optional, clumsy front-panel, GPIB
- Keithley 195A: 5.5 digit (but accuracy is more like 4.5 digit meters) LED, auto-ranging, 4-wire ohms, GPIB
- Keithley 197(A): 5.5 digit LCD, auto-ranging, 4-wire ohms, GPIB optional, -A version adds backlight
If you don't require auto-ranging, there are even more options.
You should be able to get any of these for less than $100 on ebay (a Keithley 197 just went for $80), some significantly less (search for completed auctions to get an idea about prices and popularity). Buying used does carry the risk that the equipment is broken, try to buy tested stuff. You'rE unlikely to get them calibrated unless you pay a lot more, which isn't worth it for relatively cheap meters in my opinion. As long as it's in the right ball park on all ranges, I wouldn't worry about it.
A broken calibration seal probably does mean that someone's tampered with the calibration, and they might or might not have known what they've been doing. I've broken the calibration seal because one of my meters consistently read .5 ohms low, even in 4-wire mode. After adjusting just the zero ohms calibration on all ranges, the resistance readings were within tolerance again.
As for the other two instruments, I'm also looking into purchasing a function generator and a DC powersupply. So along with the multimeter my budget for these are sadly low <=$200(I'm trying to stretch out my dollars as far as possible hoping to get relatively decent equiptment).
No suggestions, sorry. A low-frequency (up to a 100kHz or slightly better) function generator should be available cheap on ebay, eg. from Wavetek. Same for power supplies. Or you could get one of those cheap made-in-China power supplies, but don't trust them to be able to deliver their rated power. A power supply is relatively easy to build yourself, although that probably won't be cheaper if you have to buy all parts new. There hasn't been that much development in lab power supplies (unless you get into the programmable stuff), so I'd prefer an older one by a brand-name like HP to a new cheap one.
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