Old bench multimeters - Page 1
Forum section: electronics / testgear

author: jeroen79
author_rank: Frequent Contributor
timestamp: October 26, 2013, 09:37:50 pm
content: I have been looking at older (80's) bench multimeters (for example fluke 8600a, keithley 179) and see that they go for low prices (<€100) on ebay.But I was wondering about their value.How do these old bench multimeters compare to modern handheld ones?The number of digits and measurement range are similar.Is there some other way where these old units are better?Modern bench multimeters are better and more expensive as handheld ones.Assuming that this was the case in the 80's, have modern handheld multimeters caught up?And how well have they withstood the tooth of time?Are they still as accurate as they were 30 years ago?So the final question is:Is it worth buying these old multimeters?

author: JuiceKing
author_rank: Regular Contributor
timestamp: October 26, 2013, 09:48:08 pm
content: Here's one... a $5 Keithley 179A - found at the MIT Flea Market. Works great.

author: retiredcaps
author_rank: Super Contributor
timestamp: October 26, 2013, 10:01:31 pm
content: Quote from: jeroen79 on October 26, 2013, 09:37:50 pmThat all depends on what you want to do with them.The older meters have schematics, good documentation with sections like "theory of operation", parts list (BOM), "known" problems which might be fixable if they don't involve unobtainable parts, well aged parts, and tend to hold their calibration over time.

author: Unknown
author_rank: Unknown
timestamp: October 26, 2013, 10:12:10 pm
content: Modern handhelds have more features and better input protection. Old bench meters can typically measure DCV, R, often ACV and the later ones DCI/ACI. If you're lucky they might even do diodes. Rarely continuity or frequency until you get into the models released in the early nineties (eg. HP 34401A). Old bench meters were typically not designed for industrial settings (unlike many Fluke handhelds) and were designed to older (lower) safety standards. You typically won't find HRC fuses in a bench meter, for example. So I would be careful using them for mains and I wouldn't use them for anything higher.Strong point of many older bench meters are resolution, accuracy, four wire resistance, input impedance and display. You can easily get a 4.5 digit bench meter for under $100. Some 5.5 digit bench meters, like the HP 3468A, 3478A and Keithley 197, 199 are also occasionally available for under $100. This offers much more resolution and accuracy than your typical sub-$100 handheld, which is usually 3.5 digit and 0.2% accuracy or so. For comparison, the Keithley 199 is 5.5 digit and with 0.009% basic DCV accuracy. Though often not calibrated for a long time, it's not uncommon to find these meters still within or close to the 1 year specs even many years after their last calibrations. The higher resolution also often translates to higher sensitivity, especially on the voltage and resistance ranges. For example, the Keithley 199 has 1 uV AC/DC, 1 mohm resistance and 100 nA current resolution. Many bench meters will also support four wire resistance measurements (Kelvin connections), which eliminates the error caused by lead resistance (especially important for sub-1 ohm resistors). Bench meters will often have a > 1 Gohm input impedance for the lower DCV ranges. Many bench DMMs will have LED or VFD displays that have much better viewing angles and contrasts than LCDs, especially in poor light.Modern high-end handhelds (eg. Fluke 87V) have mostly caught up with the old 4.5 digit bench meters. On the other hand, an old 4.5 digit bench meter will often sell for $50 or less, much cheaper than said Fluke. Old 5.5+ digit bench meters still have better accuracy and resolution than almost any handheld meter out there.

author: SArepairman
author_rank: Frequent Contributor
timestamp: October 26, 2013, 10:25:42 pm
content: also remember old meters might not auto range

author: Unknown
author_rank: Unknown
timestamp: October 26, 2013, 10:51:26 pm
content: Many from the seventies (for example the Keithley 179) and some from the early eighties don't, but most of the later ones do. It doesn't hurt to check, though.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: October 26, 2013, 11:06:30 pm
content: Trust Alm he knows his stuff and paints a pretty accurate picture of the older meters. His point about accuracy is well made. It is often impossible or close to it to find handhelds that match the accuracy and precision (which ARE two different things) of these bench meters. I have two Keithley 199's which I love. An additional feature the 199s add on top of the 5.5 digit resolution is their scanner card which can allow you to scan 8 more connections (two wire or 4 more if your use four wire reads). A think to keep in note is that AC readings (current and voltage) on some meters was an option. It's not on the 199 but on the Fluke 8440 and I think also on the 8442 it was. Similarly, so was GPIB for remote controlling reads (standard on the 199 I think because it has the read card which needs to be computer connected to really use it to its full potential). To give you an idea of what my device can and can't do:Cans:AC VoltageDC VoltageAC CurrentDC CurrentResistance (2-wire and 4-wire)dBScanningTriggeringFilter (to filter noisy reads)Can't do:Frequency of any sortPeak holdTemperature

author: Unknown
author_rank: Unknown
timestamp: October 26, 2013, 11:29:48 pm
content: One additional point on which many bench meters (especially those intended for system applications, typically full width or half width 19" rackmount cases) perform better is sampling rate. Handhelds are usually limited to 2-4 samples/s, while many bench meters can easily do tens of samples/s. This occasionally comes in handy for adjustments, fluctuating signals or oversampling. Bench meters will usually lack the fake analog bar graph that many handhelds feature, however.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: October 26, 2013, 11:37:09 pm
content: Quote from: alm on October 26, 2013, 11:29:48 pmYou can also sometimes trade off resolution for sampling rate depending on your use. On my keithley 199 at 5.5 digits the sampling rate is 35/sec while at 4.5 digits its 64/sec. Additionally, I am pretty sure that I have seen even higher rates possible on other devices.

author: ivan747
author_rank: Super Contributor
timestamp: October 27, 2013, 12:10:35 am
content: Here's a random picture of a Keithley 191 with a banana on top of it. Don't ask why. 5 1/2 digits of resolution, 0.007% basic DC accuracy. No AC option, so it's really a volt-ohm meter but it is surprisingly useful around the lab.I think I got it for US$80 including delivery to my country, which should have been $15 or $20. I'll find the receipt tomorrow.Paid US$65 for it, free shipping to a courier in Miami, plus $15 from the courier to ship to Dominican Republic.The older basic Keithley 170 series can be very limiting, get them only if they seem functional and shipping is cheap. An old portable multimeter consider is the Fluke 27, but don't tell too many people, we don't want them to get expensive.

author: Attorney
author_rank: Regular Contributor
timestamp: October 27, 2013, 12:49:40 am
content: Quote from: SArepairman on October 26, 2013, 10:25:42 pmFor some of us, that's a good thing. Auto-ranging just slows me down when I'm trying quickly and methodically move measurement points. I've not yet seen a really fast auto-ranging DMM in any flavor.Paul

author: edavid
author_rank: Super Contributor
timestamp: October 27, 2013, 01:04:44 am
content: I like the Fluke 8600A a lot, but I'm used to paying $10-15 each for them...

author: sync
author_rank: Frequent Contributor
timestamp: October 27, 2013, 01:12:33 am
content: Quote from: Attorney on October 27, 2013, 12:49:40 amA good bench multimeter auto ranges in a few 10ms and after a sample interval the correct value is displayed. It's faster than most handheld DMM in manual rage mode.

author: Flump
author_rank: Frequent Contributor
timestamp: October 27, 2013, 01:51:46 am
content: I have a fluke 8010Aand love it to pieces, very accurate (for the amount of digits)totally rock solid, very good rf immunity as wellI also have a couple of the handheld versions too.

author: Unknown
author_rank: Unknown
timestamp: October 27, 2013, 02:38:43 am
content: Even manual ranging is nicer than on most handheld meters since bench meters either have one button per range (as in the Fluke 8010A) or a separate up and down button. This makes it much more intuitive to use than pressing range to cycle through all of the ranges as is the case on most auto-ranging handhelds.

author: SLJ
author_rank: Frequent Contributor
timestamp: October 27, 2013, 03:09:49 am
content: I love that old Fluke.Have these two on my bench. They are great buys. Paid less than $50 US for each of them and they both still match my calibrated 87V. Wish the 8800A on the bottom had pushbuttons though. Don't like the tab buttons on it. It does not weigh enough to stay in place when you push them so it's a two hand job to change ranges.

author: steve30
author_rank: Frequent Contributor
timestamp: October 27, 2013, 08:02:14 pm
content: I like old bench meters. I have an old Heathkit one and a Thurlby 1503-HA.The Heathkit one has basic functionality and is a 2000 count meter. I like it because of its highly readable panaplex displays.The Thurlby one has good accuracy and good resolution and is easy to use. Only problem is the LCD which has a slow response time.Both of these were quite cheap on ebay. The only things lacking compared to modern meters are PC interfaces, frequency measurements, auto-ranging, data logging etc. If you don't need those, you can get yourself a good bargain with old equipment.

author: Unknown
author_rank: Unknown
timestamp: October 27, 2013, 08:35:20 pm
content: System bench meters often support computer connection via a GPIB interface. Standard in some models, optional in others. Cheap ones with GPIB as standard are the Keithley 192/195/199 (note that ACV is optional in the 192 and current is absent) and HP 3455A/3456A/3478A (no current in the 3455A/3456A). GPIB interfaces are fairly expensive if you only buy them for the DMM.Some, like the HP 3456A and 3457A also have storage. One of the cheaper and smaller ones that can do data logging is the Keithley 175(A). The A adds a backlight. GPIB was optional, though.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: October 27, 2013, 08:43:56 pm
content: Any news on the Banana?

author: Napalm2002
author_rank: Regular Contributor
timestamp: October 27, 2013, 09:21:47 pm
content: Breakfast?

author: G0HZU
author_rank: Super Contributor
timestamp: October 28, 2013, 12:01:46 am
content: You can do various tricks with a bench DVM if it has a decent GPIB interface.For example, I recently bought a Keithley meter with GPIB and I've written a few Windows apps for it over the last few days. The latest app is a ToneOhm function where it reports resistance (rapidly) over GPIB and the PC mimics a toneohm in that it produces a continuously variable audio tone that lowers in pitch as you get down to a few milliohms resistance. This makes it very useful for tracing a PCB circuit for a hidden short circuit. It's really easy to program stuff like this using MS Visual Studio and I created the ToneOhm app whilst listening to the football today.It works really well with a very fast and smooth actionIt's fully programmable and can be set to auto range or to produce a dynamically changing volume (to make it less annoying than a standard Toneohm)I'm looking to add the AC current tracer function next to it. The Toneohm has this feature as standard and it should be fairly easy to make an inductive sensor for the Keithley meter and add this feature over the GPIB interface.Any decent bench DVM with GPIB should be able to do similar. You can also datalog other equipment via a DVM+GPIB with very rapid update rates.