New Keithley DMM6500 and now DAQ6510

[KedasProbe]

I made a small script to check the expected burden voltage.

It takes the maximum current in the default buffer and multiplies it with the expected resistance of the DMM6500 + 2 banana leads.
The resistance values are measured values and will vary on your unit/leads but not that much that it will lose its purpose to have an idea of the voltage drop. (for the 10A your leads will be more important to be correct)
https://github.com/Ken26M/keithley/blob/dev/Instrument_Examples/DMM6500/Check_Burden_Voltage.tsp

[Neuromodulator]

I wrote a script to measure temperature of any type of thermistor (not just the 3 available from the firmware). It uses the Steinhart-Hart equation and requires the input of the A, B and C coefficients. Hopefully someone will find this useful

Code: [Select]

dmm.measure.func = dmm.FUNC_RESISTANCE

display.clear()
display.changescreen(display.SCREEN_USER_SWIPE)

defaultA = 1.027628774E-3
defaultB = 2.393890857E-4
defaultC = 1.555947964E-7

a = display.input.number("Coefficient A", display.NFORMAT_EXPONENT, defaultA)
b = display.input.number("Coefficient B", display.NFORMAT_EXPONENT, defaultB)
c = display.input.number("Coefficient C", display.NFORMAT_EXPONENT, defaultC)

button = display.input.option("Unit", "\19C", "\19F", "\19K")

while (true)
do
    logR = math.log(dmm.measure.read())

    kelvin = 1. / (a + b * logR + c * (math.pow(logR, 3.)))
    celsius = kelvin - 273.15
    fahrenheit = (celsius * 9. / 5.) + 32.

    if (button == display.BUTTON_OPTION1) or (button == nil) then
        text = string.format("%.3f \19C", celsius)
    elseif button == display.BUTTON_OPTION2 then
        text = string.format("%.3f \19F", fahrenheit)
    else
        text = string.format("%.3f \19K", kelvin)
    end

display.settext(display.TEXT1, text)
end



[gby]

I was using my DMM6500 from the front contacts to measure current.  I had the range set to 3.0 A (auto scale turned off).  I used it successfully for quite a while when an accident led to a high current spike.  Now the DMM6500 white current to common is open circuit.  Fine, I thought, I must have blown the fuse so I twisted the white contact out and checked the fuse.  Fuse looked fine and Ohm meter shows a short.  But after replacing it into the socket the current range is still open circuited.

It acts like something was blown open circuit in the current measurement path inside the instrument....yet the small 3 A fuse inside the contact that is supposed to protect the instrument is fine.

Is there another replaceable fuse somewhere inside the DMM6500?  Any clues how to fix this?

If there is nothing simple I can fix I guess I will have to return the unit to Keithley for repair.  Since it is only 1 year old I assume it would be warranty repair?

[KedasProbe]

Maybe some other fuse inside blow first.
You should ask their tech support, they will most likely know what most likely happened.

[HKJ]

There is a 3.5A 1000V fuse inside, you can see it just before the metal cover on this picture:


You can see many more pictures in my review: https://lygte-info.dk/review/DMMKeithley%20DMM6500%20UK.html

[gby]

Thanks for the hint and picture HKJ.  I will check it out next week when I am back in the office.  Hopefully it is just that fuse and hopefully they are not hard to order nor real expensive.

[FrenchieRaf]

Hi all,
Thanks everyone for this very interesting thread full of valuable information.

May I ask the happy owners of this meter, on the first page Mr Krampmeier said he was worried about the time for switching between measurement functions, has this been fixed?

Do someone know of a video showing this?

For EU folks, what's the cheapest online price including taxes for it?
Thanks!And cheers from France 

[exe]

Feature requests: make unit shorter and remove fan if possible .

PS I understand that a single-pcb construction and compatibility with old scanner cards could play a role here.

[drummerdimitri]

I have a couple of question regarding the shunt resistor values for a given measurement.

If for example I am using a shunt resistor rated for 100 A 75 mV does that mean it is safe to use up to 100 A or does it just mean that at 100 A the voltage drop across it will be 75 mV?

Also, can I use the 100 A shunt for lower than 1 A draws or will that result in an inaccurate power reading? What's a good rule to go by?
 

[jjoonathan]

Is there a way to get DCV + ACV readings at the same time without the relay constantly clicking between them?

[drummerdimitri]

Is there a way to get DCV + ACV readings at the same time without the relay constantly clicking between them?

There are some ranges where they use the same shunt resistor such as 10V and 1A range with a couple of other ranges otherwise you will have to wear those relays out.

[jjoonathan]

Yeah, I saw that discussion when cruising through the thread search for "relay," but that's for voltage + current whereas I'm looking for voltage + voltage. I'd be perfectly happy with a similar solution but even after a bit of fiddling with the ranges I still haven't been able to figure out a click-less combination.

[KedasProbe]

For EU folks, what's the cheapest online price including taxes for it?
Thanks!And cheers from France 

I saw Farrell is selling it cheap. 808euro (excl. tax)
I also saw conrad.fr is more expensive than conrad.de or .be

edit www.conrad.it is 867 (excl. tax)

[KedasProbe]

Yeah, I saw that discussion when cruising through the thread search for "relay," but that's for voltage + current whereas I'm looking for voltage + voltage. I'd be perfectly happy with a similar solution but even after a bit of fiddling with the ranges I still haven't been able to figure out a click-less combination.

The only good solution to avoid relays is to buy 2 DMM6500 

[Kleinstein]

For AC + DC there is in theory a way: use the digitizer mode and statistics functions: The average voltage gives the DC value and the std. deviation is equal to the RMS for pure AC. The geometric sum gives AC+DC RMS - this could likely be done in a short script.

[JxR]

Is there a way to get DCV + ACV readings at the same time without the relay constantly clicking between them?

The 1A/3A/10A ranges will result in no clicking.  The voltage can be left on Auto, or any range you choose.

[jjoonathan]

I am after AC/DC, not I/V 

Yeah, I saw that discussion when cruising through the thread search for "relay," but that's for voltage + current whereas I'm looking for voltage + voltage. I'd be perfectly happy with a similar solution but even after a bit of fiddling with the ranges I still haven't been able to figure out a click-less combination.

The only good solution to avoid relays is to buy 2 DMM6500 

You probably meant that as a joke, but right now I have my DMM6500 in parallel with my 34401a for exactly that reason.

For AC + DC there is in theory a way: use the digitizer mode and statistics functions: The average voltage gives the DC value and the std. deviation is equal to the RMS for pure AC. The geometric sum gives AC+DC RMS - this could likely be done in a short script.

It might just come to that.

[JxR]

I am after AC/DC, not I/V 

Opps, didn't catch that.  Yeah, there is no range you can select as far as I can tell that will not result in the relays clicking.  Anyways, what you are already doing is probably your best bet.

Although if you don't need fast measurements for both ACV/DCV you could probably put a long delay on one of the measurements to lessen the relay switching (or put a delay on both).

[jjoonathan]

If I knew how to configure the relay delay, I'd decrease it for more lively updates. The default configuration is no good for browsing.

The problem here is that I factored selling the 34401a into my purchase justification. The buyer's remorse is hitting pretty hard right now.

I know, I know, I'm the dumbass for not finding a datasheet line where they wrote in blood that their 1MS/s digitizing multimeter with a secondary measurement display can actually simultaneously measure the AC and DC content of a waveform at > 1S/s.

Ugh. 

[KedasProbe]

The maybe future FFT app may also give you your DC and AC. (assuming they make it right)

On the other hand, what is the lifetime of these relays at such low freq 1Hz. (1 000 000 to 10 000 000 operations?)
obviously we don't want to break them but aren't we over-cautious?

[Mr. Scram]

What's the deal with the Keithley 2000 being sold new at higher prices than the DMM6500? Are there reasons to stick with the Keithley 2000? Less noise?

[exe]

What's the deal with the Keithley 2000 being sold new at higher prices than the DMM6500?

Greediness.

[Mr. Scram]

Greediness.

The same shops carry both, so I guess that's not it.

[exe]

The same shops carry both, so I guess that's not it.

Wow, I thought you were talking about NOS on ebay, not shops... Didn't know it's still on sale, I thought it was obsolete more than 10 years ago. Amazing.

[ruffy91]

Most probably the newer DMM was designed with a cheaper BOM and more modern/better components.