Author Topic: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?  (Read 5080 times)

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Offline colorado.rob

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #100 on: September 19, 2020, 01:35:57 am »
I own a Siglent SDM3065X.  I do a bit of lab automation with PyVISA.  I use this instrument quite a bit for automated programming and diagnostics.

This is my first bench meter so I don't have reference for comparison with other brands or models.

My only gripe with the meter is that the optional scanner card cannot be added after purchase.  I didn't realize at the time that this is something that would become useful for me to have until a couple of years after owning and using the meter.  I am now considering selling the one I have on the second-hand market and buying a new one with a scanner card.  I would prefer being able to send it in to Saelig (where it was purchased) or Siglent NA and have them retrofit the option.


 

Online tautech

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #101 on: September 19, 2020, 01:45:47 am »
I own a Siglent SDM3065X.  I do a bit of lab automation with PyVISA.  I use this instrument quite a bit for automated programming and diagnostics.

This is my first bench meter so I don't have reference for comparison with other brands or models.

My only gripe with the meter is that the optional scanner card cannot be added after purchase.  I didn't realize at the time that this is something that would become useful for me to have until a couple of years after owning and using the meter.  I am now considering selling the one I have on the second-hand market and buying a new one with a scanner card.  I would prefer being able to send it in to Saelig (where it was purchased) or Siglent NA and have them retrofit the option.
Sadly not possible.
On one I looked at a few years ago was missing the physical mounting HW and connection looms and componentry for the SC.

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Offline skullan

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #102 on: September 19, 2020, 02:09:05 am »
I can say a reason why I won't have one at home, is purely due to the "Omg, where the hell do I plug THIS in".
 

Offline bikeNomad

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #103 on: September 19, 2020, 05:44:26 pm »
I have two Fluke 8840A and one Fluke 8842A meters.
These are remarkably accurate, even many years out of calibration (I've compared with in-cal bench meters at work).
Their disadvantages:

  * VFD displays (I'm making an LED replacement display)
  * no AC+DC RMS readings
  * no continuity buzzer (my LED replacement display will provide this)
  * Can't leave the 4-wire ohms test leads in for other uses (SENSE terminals aren't disconnected in non-Ω ranges)
  * auto-ranging sometimes gets confused
  * current measurement isn't that great
  * AC measurement and IEEE-488 comms are optional (though my meters have both)

I end up using my Fluke 287 handheld DMM for a lot of general purpose work but its start-up time and lack of an AC power supply annoy me.
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Offline Wytnucls

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #104 on: September 23, 2020, 07:04:34 am »
I just took apart an old 8842A that apparently was connected to excessive voltage--at least 1500V---with some power to back it up.  The entire front end protection--4 MOVs and 2 fusible resistors--were incinerated.  I removed the burnt parts and subbed in 2 regular 1K resistors (to be repaired properly later, of course) and the meter works properly and is in cal.  No evidence of any external damage, the circuit board is unharmed (but sooty)  and I'm sure nobody died.  I'd say that is 'robust' although I can't quantify that.

Nowhere in CAT documents does it say the the meter should survive.

Again, 61010-2-033 section 14.101 states:  "The component shall not rupture and shall operate as intended during the test."   

IMO, operate as intended means just that, the DMM continues to read properly. 

One of the tests I have shown several times is from section 101.3.2.   The criteria, "During and after the test, no damage to the equipment shall occur."  IMO, that's not the test equipment being used to test the DMM they are referring to, it's the DMM.

"After the voltage of 4.4.2.101 has been applied to the METER, the METER shall continue to be
able to indicate the presence of HAZARDOUS LIVE voltages up to the maximum RATED voltage.
NOTE The METER is not required to maintain its normal accuracy. A maximum deviation of 10 % is acceptable."

Of course there are many other cases as I have mentioned before.  But again, just to be clear, this is outside of my area and I am providing my interpretation of what the standard states.    I would find it hard to believe for example that the pass fail criteria for an impulse test would be if the combo generator was damaged or not.    Fungus may see it otherwise.   

That said, I would imagine that some of the meters I have looked at would pass both the safety and EMC standards with a wide margin but there are far more that wouldn't come close.

You are taking statements out of context.

'The intent of the standard is to ensure the safety of the operator and surrounding area.
Performance / functional requirements are not covered by the standard'. (1)


101.3.2 deals with the fuse protection on the A/mA ranges. Of course no damage should occur, as a conductive path or spark for 1 minute with a 2000V test applied, would cause havoc and affect the safety of the operator.

4.4.2.101 refers to the voltage (1100V AC) applied to voltage measuring terminals in single fault conditions 4.4, (with either MOV or current limiting resistor shorted). The meter must be able to display the presence of a hazardous voltage in a damaged condition (safety consideration).

As for 14.101 (10 high voltage transients), the standard requires that no hazard shall arise due to the operation of overvoltage limiting component.
The component (MOV, sparkgap) shall not rupture and shall operate as intended during the test.
If the component is heated as a result of this test, it shall not heat other materials to their ignition points.
There is no concern for the serviceability of the meter after the test. (It may or may not survive)

(1) Claudia Sirch is the global chief engineer for medical, laboratory, measurement and control equipment and laser products at Intertek. She has over 25 years of experience in the testing and certification business, and is a lead and technical assessor in the IECEE CB Scheme.  She holds a Bachelor of Science in Engineering Physics from Munich University of Applied Sciences.
« Last Edit: September 23, 2020, 01:53:50 pm by Wytnucls »
 

Offline TiN

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #105 on: September 23, 2020, 07:46:53 am »
Keithley 2002

* Shrouded banana jacks. Would prefer low-thermal 5-way binding posts so much...
* Hot
* No electronically controlled front/rear switching

HP/Agilent/Keysight 3458A

* Poor resistance performance compared to competition
* No electronically controlled front/rear switching

Datron 1281

* No NPLC control => poor speed/perf flexibility
* Not really a disadvantage, but complex calibration procedures :)
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Offline AVGresponding

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Re: What are - for you - the 3 biggest disadvantages of your benchtop DMM(s)?
« Reply #106 on: September 23, 2020, 05:08:50 pm »
Keithley 2002

* No electronically controlled front/rear switching


HP/Agilent/Keysight 3458A

* No electronically controlled front/rear switching

Depending on your POV this can be an advantage; I recently picked up a Keithley 2000 quite cheap, as it was showing errors 600:1 and 600:2, which turned out to be just the switch needing cleaning (calculated risk I know).
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