Continuity on HP DMMs? - Page 1
Forum section: electronics / testgear

author: echen1024
author_rank: Super Contributor
timestamp: August 05, 2013, 09:14:54 pm
content: I was browsing ebay for some old HP DMMs, and noticed that only the newer 34401s have continuity. I am ideally looking for one under $300USD that can measure Temp and Continuity. The 3457 seems like a good choice. Any input?

author: Unknown
author_rank: Unknown
timestamp: August 05, 2013, 10:17:31 pm
content: The old system DMMs (19" wide) were generally limited to the basics: AC/DC voltage, resistance and if you're lucky current. Fluke even had a meter where only DCV was standard, everything else (ACV, resistance) was optional. I guess that was useful back when these features were expensive if you needed a dozen meters to measure resistance.The temperature feature that you'll find on older bench meters will generally be RTD or thermistor based. I.e. resistance measurement with some math to convert it to temperature. Don't expect to plug a type K thermocouple in there.The lower end bench meters with less resolution, i.e. the Fluke 8000 form factor, would sometimes have more features like continuity and diode test, since these were often used for field service work before the handheld became powerful enough to handle those tasks. These were generally limited to 4.5 digits of resolution. I think the HP 34401A and the Keithley 2000. I believe of those two only the Keithley supports cheap thermocouples.Do you really need to combine these features in the same box? You don't really need 6.5 digits for temperature or continuity.

author: echen1024
author_rank: Super Contributor
timestamp: August 05, 2013, 11:59:42 pm
content: I understand, but I just wanted a bench meter with some of the features I use frequently. I am also quite fed up of forgetting to turn my DMM off.

author: Fsck
author_rank: Super Contributor
timestamp: August 06, 2013, 12:17:23 am
content: Why would you turn a bench dmm off? it's easier to leave them on, plus they'll be stabilized for immediate use instead of you having to wait 1-4 hours for the meter to fully stabilize. (unless you're only using like 4.5 of those digits, in which case there's no need for a bench dmm)since you most likely will need 2+ meters for use anyways, just have your second meter with temp and continuity.

author: echen1024
author_rank: Super Contributor
timestamp: August 06, 2013, 12:21:26 am
content: I have a shit handheld. I keep on forgetting to turn that one off.

author: Unknown
author_rank: Unknown
timestamp: August 06, 2013, 07:25:04 am
content: Auto power off works decently on good handhelds. Not the UT-61E, though.You may be able to find a 3.5/4.5 digit bench meter in the old Fluke/HP/Keithley models with continuity and temperature. Otherwise there are the new low-end bench meters / lunch boxes that you may be able to find under $300 that might have these features.

author: dzseki
author_rank: Frequent Contributor
timestamp: August 06, 2013, 07:56:44 am
content: I have a handheld DMM on my bench as well, I simply made an extender for the battery cable so I run it from an external 9V supply, cheap and simple trick

author: Unknown
author_rank: Unknown
timestamp: August 06, 2013, 08:09:04 am
content: Just don't use it near any circuit containing voltages above 50 V or so like that, especially mains.

author: dzseki
author_rank: Frequent Contributor
timestamp: August 06, 2013, 08:20:29 am
content: Quote from: alm on August 06, 2013, 08:09:04 amWell I have to admit that nowaydays this only a spare meter, as I bought a proper bench DMM, but back in the day I measured with that 1,5kV (in the 1000V range) without any problemIt's a Chinise DT9205A multimeter (one of the cheapest ever).The EU standard specify for every mains appliance that they have to stand 1,5kV (the old Hungarian standard was 2kV) between the primer / secunder windings. I guess my mains adapter meets this requirement, it was a Sony crt tv's standby psu... Otherwise it is a rare task to meaasure anything over 100V on a bench IMO.

author: Unknown
author_rank: Unknown
timestamp: August 06, 2013, 08:28:25 am
content: But even a CAT I 1.5 kV meter would probably need an isolation rating of several kV. And just because it's supposed to protect you if 1.5 kV came in via mains (I don't trust some of those power supplies to even survive 230 V, let alone higher), does not mean the isolation of the low voltage side has anywhere near that rating. Look at the power supply for a Fluke ScopeMeter to get an idea what's involved.

author: echen1024
author_rank: Super Contributor
timestamp: August 06, 2013, 03:13:00 pm
content: The highest I'm probably going to ever go is 120V on the mains. I don't think I will be playing around with HV that often.

author: ddavidebor
author_rank: Super Contributor
timestamp: August 06, 2013, 03:25:15 pm
content: The problem are transients