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Fluke 185 Review

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mimi123:

--- Quote from: Wytnucls on June 22, 2015, 06:58:34 pm ---Replacing a MOSFET shouldn't need calibration, as it is just used as a switch.
Calibration is performed through the IR port, with 5520A calibrator. Sorry, I don't have the exact procedure for the calibration mode.

--- End quote ---

Thank you anyway.

I forget to mention the original mosfets of my Tektronix TX3 (Q100 and Q101) are L2203NS, the same as the Fluke.

I think that as these mosfets are used to switch the shunt resistor(5mohms) any difference in their Rdson should change the measure because the two mosfets are both in parallel and then in series with the resistor.
L2203SN has 7 mohms and the IRF3205 8 mohms, but this is the maximum value that says the data sheet, real value should vary quite from part to part and with it the measurement.
Has this sense to you?

I think I've been very lucky with the result.

Another story is the consumption while in standby (OFF). I measure 40 uamps.   I think is for the gates of these mosfets that has 9volts when in off mode.

I read this consumption here but now I can't find it.

Did you measure it?





Wytnucls:
No, I haven't measured current consumption in STBY mode. 40uA doesn't sound like much anyway.

One thing I have measured is the true RMS voltage of a train of pulses and I get strange results on the 185.
There might be a good technical reason for the discrepancy or my meter is faulty.
I'd appreciate your trying the same test, if you have a function generator:
5 pulses of 20uS each 50%, 5Vpp with 2.5V offset and 300uS period.

Here are my results, compared to other DMMs (AC+DC):



Noise Floor:

--- Quote from: cluca1969 on April 05, 2015, 08:39:04 pm ---Hi Noise Floor,
I'm glad to hear that about your Fluke 185. I just bought 185 a few days ago. I paid 250 euro, a little too expensive for a old Fluke model, but is MADE IN USA.
Can you tell me in a few words about this model of Fluke, information are quite a few on web. A few pros and cons you have over the years (calibration, accuracy, other problems encountered with it).
With special consideration,
Lucian Cernega.

--- End quote ---

Sorry for not responding earlier, I sometimes forget to check on threads I've posted in. :)
Pros - Durability (survived several drops), Battery life (better or on par of other handheld meters I've had, Accuracy been "good enough" for my troubleshooting testing I've done with it when calibrated
Cons - The display not always easiest to read (Got an OLED unit so I'm spoiled now), Cost was a little higher than competitor products

mimi123:

--- Quote from: Wytnucls on June 23, 2015, 12:57:00 am ---No, I haven't measured current consumption in STBY mode. 40uA doesn't sound like much anyway.

One thing I have measured is the true RMS voltage of a train of pulses and I get strange results on the 185.
There might be a good technical reason for the discrepancy or my meter is faulty.
I'd appreciate your trying the same test, if you have a function generator:
5 pulses of 20uS each 50%, 5Vpp with 2.5V offset and 300uS period.

--- End quote ---

Sorry I don't have a function generator like yours. I can measure a square wave if is useful for you.
Did you select the bandwidth at the generator?
If not maybe the problem is here. The Fluke seems to have a lower BW.

Wytnucls:
Yes, you could try a 4V square wave 20kHz 50% with no offset in AC mode only.
I get 1.8297 instead of 2V on the other meters.
Either the bandwidth is over optimistic or my meter is faulty.
Reducing the frequency gives a more accurate result. At 2kHz, the measurement is correct.

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