Hameg HMC8012 and Keysight/Agilent 34465A - Page 1
Forum section: electronics / testgear

author: Nozzer
author_rank: Contributor
timestamp: May 21, 2016, 06:05:48 pm
content: I have been looking at both these DMM and like features of both. For my purposes the 34465A better suits my needs, however there is one feature of the HMC8012 I really like and would find useful. That is the secondary measurement, viz the ability to measure DC Volts and DC Current at the same time, plus display the Power. The 34465A offers the ability to measure DCV and DCI at the same time, but displays the DCI as volts in their secondary peak-to-peak display.I wonder if Keysight will consider updating their software to offer the DCV, DCI and Power display on their DMM?

author: TheSteve
author_rank: Unknown
timestamp: May 21, 2016, 09:34:27 pm
content: Are you sure the 34465A can measure DCV and DCI at the same time? The 34461A can only do DCV and ACV at the same time.

author: nctnico
author_rank: Super Contributor
timestamp: May 21, 2016, 10:26:39 pm
content: Either way the DMM will need to switch between the current and voltage inputs continuously which could wear it out quickly. How about getting 2 multimeters connected to a PC to calculate power?

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 21, 2016, 10:46:55 pm
content: Hi,the 34465A/470A definitely do not measure DCV and DCI simultaneously!Neither in DCV nor DCI mode, the other function is available as secondary measurement.I think, one Keithley had this feature, but it did so by permanently switching a relay, which sounded not very healthy.As DCI and DCV internally have a common ground in most DMMs, I think it's very critical to use this function, as this may produce errors inside the DUT circuit.I'd always prefer 2 separate instruments.Frank

author: nugglix
author_rank: Regular Contributor
timestamp: May 22, 2016, 06:59:22 am
content: Quote from: nctnico on May 21, 2016, 10:26:39 pmCould you explain that, pls?

author: tautech
author_rank: Super Contributor
timestamp: May 22, 2016, 07:31:33 am
content: Quote from: nugglix on May 22, 2016, 06:59:22 amIn Dual measurement mode a relay switches back and forth between the selected dual/double measurement inputs @ ~1/sec. These are generally a 3 wire connection setup but AFAIKT it's switched deep within the meter and the physical connection isn't broken by the relay only the connection to the selected dual measurement functions. In this way there should be little loading of the relay contacts and only the mechanical life of the relay will determine the useful service life of a meter during prolonged dual measurements.Thinking back I've not seen any relay failure threads in meters doing dual measurement, but there probably are.Somebody will probably link one and prove me wrong.For the OP a SDM3055 has a range of dual measurement capabilities.https://www.eevblog.com/forum/testgear/siglent-new-bench-dmm-sdm3055/

author: nugglix
author_rank: Regular Contributor
timestamp: May 22, 2016, 08:35:31 am
content: Quote from: tautech on May 22, 2016, 07:31:33 amHmm... my HMC8012 doesn't click any relays.And the update seems to be faster than 1Hz.It seems the assumptions above are just that: assumptions.Now waiting for the post that demands that I have to prove my point...

author: tautech
author_rank: Super Contributor
timestamp: May 22, 2016, 08:56:56 am
content: Quote from: nugglix on May 22, 2016, 08:35:31 amNice, a bench DMM that doesn't use relays for dual measurements.FYI most do.$875 vs $469 for SDM3055 you'd expect some snazzy features.

author: nugglix
author_rank: Regular Contributor
timestamp: May 22, 2016, 09:08:59 am
content: Quote from: tautech on May 22, 2016, 08:56:56 amHard to believe that the even more expensive meters can't do that.Ordered mine just at the moment before the Euro went down (and therefore the prices up).Saved ~€100 that way.Thanks to the price change I got a calibrated one for the old price, they hadn't changed that.And for the records: the HMC8012 is a nice meter; might not have the highest resolution butwrt features and usability it's well worth the money.And it features the same look for the buttons and knobs as my oscilloscope.

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 22, 2016, 09:28:15 am
content: Quote from: nugglix on May 22, 2016, 08:35:31 amCan you please verify, if the HMC8012 DCV and DCI measurements have a common ground, or not?Is this specified somewhere?This feature would require at first separate ground jacks for DCI and for DCV, and also a real differential input amplifier in the front end, which I think both are very improbable.The relay for DCI mostly is necessary, if the instrument has high current ranges like 0.1A, 1A, 3A in addition to low current ranges, which can not be switched so easily by FETs.Frank

author: owiecc
author_rank: Frequent Contributor
timestamp: May 22, 2016, 09:52:35 am
content: Quote from: Dr. Frank on May 22, 2016, 09:28:15 amSwitching 10A with a power FET is easy.

author: TopLoser
author_rank: Unknown
timestamp: May 22, 2016, 09:58:18 am
content: www.youtube.com/watch?v=87fBaqPyhCs#action=shareReview here shows it measuring voltage and current at the same time, round about the 8 minute mark.

author: nctnico
author_rank: Super Contributor
timestamp: May 22, 2016, 10:44:47 am
content: Quote from: nugglix on May 22, 2016, 08:35:31 amWell, there are a whole bunch op relays inside it:https://www.eevblog.com/forum/testgear/hameg-hmc8012-porn/msg320521/#msg320521Unless a multimer has 2 (or more) ADC sections it can only measure one input at a time.@Dr. Frank: the relays only switch between the DC input and burden resistors so they don't carry large currents (preferably no current at all).

author: nugglix
author_rank: Regular Contributor
timestamp: May 22, 2016, 11:58:56 am
content: Quote from: Dr. Frank on May 22, 2016, 09:28:15 amThere is only one ground, so I think it's save to say that this is common.Would have been easy to see on a random picture of the meter.Btw, the manuals are available online -- just in case...No clicking, no nothing.For what I did see attached pics.Quote from: nugglix on May 22, 2016, 08:35:31 amObviously I'm able to predict the future...

author: 1design
author_rank: Regular Contributor
timestamp: May 22, 2016, 03:34:02 pm
content: The unit is packed with silicon switches so that is how they do the switching.MAX338ADG633etc.BR

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 22, 2016, 03:35:32 pm
content: Quote from: owiecc on May 22, 2016, 09:52:35 amOn first thought only!In comparison to relays, with a FET (switch) you have to take care about:- reversing the current flow- over current protection- protection against load dump pulses (inductive loads)- gate leakage currents (for precision measurements)Frank

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 22, 2016, 03:42:24 pm
content: Quote from: nugglix on May 22, 2016, 11:58:56 amYes, I also had a look in to the manual, on page 20 there's a nice application of simultaneous current and voltage measurement, i.e. it can also measure power consumption.For some reason, they demonstrate this feature for low currents only.For this schematic, one directly sees the big limitation of common ground, that is the big measurement error for higher currents, as you always include the ground cable , and cannot compensate for the voltage drop across it, i.e. no real Kelvin connection possible.So it may be a nice feature, but really with limited possibilities.Frank

author: nugglix
author_rank: Regular Contributor
timestamp: May 22, 2016, 05:37:22 pm
content: Quote from: Dr. Frank on May 22, 2016, 03:42:24 pmI've no need for high currents and therefore I still consider this a useful feature.This "limit" sounds contrived, given that this is no high-end meter.Case closed.

author: TheSteve
author_rank: Unknown
timestamp: May 22, 2016, 05:52:01 pm
content: It's a nice feature but don't expect to find it on a precision multimeter.

author: Nozzer
author_rank: Contributor
timestamp: May 26, 2016, 04:20:38 pm
content: Thanks for all your helpful replies.The Keysight can be used to measure both DCI and DCI according to the video by Keysight below.https://youtu.be/Y6xnLkiUMn8That's why I wondered if they would consider doing the same display implementation as the Hameg. Looks like I'll be buying both!The source of my info for the Hameg was the Watt Circuit video below [8 minutes in].https://youtu.be/87fBaqPyhCs

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 26, 2016, 06:29:13 pm
content: Quote from: Nozzer on May 26, 2016, 04:20:38 pmWell, the 34465A only can do it indirectly, by using its feature to measure two voltages simultaneously in ratio mode.But you cannot use its DCI mode and ranges, that was the discrepancy..(and a great pity)This trick is limited to +/- 12V on the sense lines, but your ground potential for the voltage measurement can also be off by that amount, that's the advantage over the other instruments, which have one common ground.Thanks for that hint to the Keysight video, I haven't seen it before. This simultaneous measurement can be done much better, with correct DCV measurement, if you chose the potentials correctly.Btw.: I can highly recommend the 34465A for its precision and the other versatile possibilities, especially the great DCI ranges of 1µA ... 10A (F.S.)You also should get the Digitize function, 2MB memory currently is free.Frank