Keithley 177 in Japan (100v, 50Hz) - Page 1
Forum section: electronics / testgear

author: michael@metgen.tech
author_rank: Contributor
timestamp: December 04, 2022, 03:17:57 am
content: I had some help deciding to by a Keithley 177 for use in Japan (100v, 50Hz), a couple of years ago. Having saved USD 20 on postage (meter was on USD 38), thanks to a colleague offering to bring it over, now that C19 restrictions have been somewhat relaxed I finally have my DMM (only 2 years after the original purchase and with an obviously new crack in the case). Anyway, I have a few questions and could use some help please:1. The device has a three pin plug and I only have 2 pin power. I presume that, given it's an AC input anyway, the polarity doesn't matter? Most Japanese plugs have two identical pins but I can find a US style one with a fat pin if necessary. Before anyone comments, there is never an earth on normal Japanese home wiring. I have tried plugging it in the "right way round" and the lights come on and numbers show.2. Using a somewhat aged DMM for the first time, what do you recommend that I do to check that it's working? After powering on, for example, adjusting the zero knob doesn't seem to change anything but there were no leads anyway, so not sure that means much as yet.3. If it's out of whack, is it worth getting it calibrated and is that even possible these days?Thanks!Mike

author: TimFox
author_rank: Super Contributor
timestamp: December 04, 2022, 03:48:20 am
content: You can use a US-style 3-pin to 2-pin adapter, but please connect the ground screw/strap/wire on the adapter to a decent ground for safety.

author: michael@metgen.tech
author_rank: Contributor
timestamp: December 04, 2022, 04:25:02 am
content: Thanks for advice but doesn't quite solve my problem. I think that I'm actually going to change the cable entirely. In any event, there is no "decent ground" or any ground, for that matter, available in my apartment.Pretty much everything here is double isolated and doesn't have a ground connection. Using things that do require ground can be a bit nerve wracking. I don't think that I want to strap ground to Neutral, although that may not be the worst option.Ultimately I'm not going to be using this meter with any serious voltage anyway, so safety probably isn't a major issue... until it is. I am not 100% clear on what the Ground protection provides protection from: mains leaking into test cables, checking too high a voltage... or what? Or is it just a matter of not being double insulated and having the opportunity to earth the whole thing (the case is plastic anyway).

author: michael@metgen.tech
author_rank: Contributor
timestamp: December 04, 2022, 09:13:22 am
content: Appears meter not working anyway, so bigger problems to solve first... Hey ho. Thanks!

author: AVGresponding
author_rank: Super Contributor
timestamp: December 04, 2022, 10:09:06 am
content: The manual indicates an earth ground is required for safety; looking at the schematic implies this is connected only to the power transformers frame and screen. Using it without one shouldn't make it any more unsafe than any other class 2 appliance in your house, but there might be some noise on the supply, which may or may not affect the performance when you're playing around in the uV ranges.There are some barely readable scans of the manual out there, xdevs has a clear one.

author: J-R
author_rank: Super Contributor
timestamp: December 04, 2022, 08:58:55 pm
content: Maybe you could make a ground for your bench by connecting to plumbing or by running a wire outside to a ground rod?

author: lowimpedance
author_rank: Super Contributor
timestamp: December 04, 2022, 11:42:50 pm
content: Quote from: michael@metgen.tech on December 04, 2022, 09:13:22 amApply a little contact cleaner/lube into the open ends at the rear of the switches and 'exercise them' a number of times to help break down any oxidation of the internal contacts.Those switches have probably not moved in years ! (more than just the two you were waiting as well).I'll bet the internal 2A current fuse has been popped too !

author: michael@metgen.tech
author_rank: Contributor
timestamp: December 05, 2022, 03:36:16 am
content: Thanks. Power button a bit unreliable but lights do come on. Decimal point moves with range changes but the numbers don't change (using trim or probes) at all, although there are different every time you turn it on.As suggested, I'll try the contacts first and check the fuse.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 05, 2022, 06:33:32 am
content: Quote from: J-R on December 04, 2022, 08:58:55 pmYou don't make a double insulated system safer by adding an external ground reference point.@OP are you using this in Japan, or the US?

author: J-R
author_rank: Super Contributor
timestamp: December 05, 2022, 07:51:38 am
content: So if there is a fault with a non-double-insulated device, it is safer if you are the path to ground, rather than a grounding rod, got it.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 05, 2022, 12:36:55 pm
content: Quote from: J-R on December 05, 2022, 07:51:38 amPersonally I wouldn't work on such an item without a CPC integrated into the fixed wiring, and an RCBO protecting the circuit. Making the workbench the path to ground is a bad idea, since there's a fair chance that you'll be the link between the DUT and the bench at some point.For this particular piece of TE in this particular circumstance the safest way to use it is just to not bother with the CPC, since its only apparent function is to connect the transformer interwinding screen to earth ground.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 05, 2022, 06:03:32 pm
content: The Japanese electrical system is a 200V split-phase (for 100V per leg) system with earth leakage breaker protecting all circuits in every system I've seen so far (including decades old installations).Running the device without an earth should be ok IMO with suitable precautions (but I do not recommend it if the user is not familiar with electrical safety) and basically the only way to do so in most houses here in Japan, unless using the gear in the kitchen or laundry areas where the only earthed outlets are usually located, if the building isn't too old...I opted to get all consents (Japanese for power outlet) earthed when I built my house but not everyone has that luxury.If the OP lives in a mansion (Japanese for apartment block or condo), it may not be possible to run an earth wire to an earth stake in the ground. Finding an earthed outlet or water pipe may be the only way.The other option would be an isolation transformer, they are available from Akihabara etc, or mail-order if not near a suitable electronics store.