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AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter

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Fungus:

--- Quote from: ModemHead on September 07, 2017, 12:20:28 pm ---The Ragu sauce/measure unit is now up to $14.99 at amazon this morning.

--- End quote ---

The cheap ones seem to have gone from eBay, too. With shipping there's no way I could get one for less than about $50 now.

Three times the cost of the meter this thread is supposed to be discussing and more than a Fluke 101? No thanks.

stj:
it would be interesting if they used the 1106 chip,
someone should bump it to 10,000 count in the eeprom and then see if the AC true-rms readings still look o.k.

ocw:

--- Quote ---On every DTM0660/DM1106EN meter I've tested so far, the -3dB point is 3kHz. But this one is only 1dB down at 2.6kHz?
--- End quote ---

I double checked that.  The Ragu 17B+ -1% voltage figure again was 1.6 kHz.  However the -1dB figure was 2.24 kHz this time.  I repeated the process several times--2.24 kHz is the correct figure.  I will correct my other message.  The voltage measurement was -3dB at 3.05 kHz.

I completed my accuracy verification of the 17B by measuring its AC current accuracy.  The uA AC readings were +/-0.1% while the mA readings were around +0.6%.  The A readings were about -0.3%. 

Similar to my voltage accuracy tests, I tested the current at 1X, 2X, 4X, 6X, 10X, 20X, 40X, 60X... points.  I precisely measure the output voltage of my audio generator and set the current by the proper choice of a 0.01% current limiting resistor.  This simulates the way that I most frequently use to meter to measure current--measuring the current from a voltage regulated power supply.  I mathematically correct that reading to see if it then matches the manufacturers specifications.  But, more importantly is how accurate the meter is without correction.  I feel that at least the moderate and higher price meters should not use an outdated VOM current measurement accuracy standard. 

For higher current evaluations I measure the voltage drop across four terminal precision resistors to determine the current being measured.  I make the tests at 60 Hz.  The current measurements most frequently have frequency response similar to that for voltage measurements.

floobydust:
What's weird is how the factory CAL is done. You'd think it was automated.
But I can't see any calibration/test points on PCB, other than a soldered 0805 CAL jumper.
No serial data in/out. So not sure how data is being written to the EEPROM.

For the capacitance (null) calibration, it is funny the EEPROMs copy the "Uni-T" or "Brymen" number and use that for the stray capacitance value. Nobody seems to actually come up with the real value, only copying it.

This is what I have on the capacitance CAL:

Capacitance correction (500.0nF, 50.00uF)
The measurement function of the calibration table switch is placed in the capacitor position (or the resistance level (J1A, J1B short circuit)).

Calibrator output 500.0nF, wait for the display is stable, press +/- to adjust to 500.0 nF;
Can be used for the correction of the output value: 200nF ~ 600nF (100nF integer times), the recommended value of 500.0nF.

Calibrator output 50.00uF, wait for the display is stable, press +/- to adjust the display to 50.00 uF. If it has been adjusted, Press SELECT to skip this adjustment.
The capacitance value that can be used for correction: 20uF to 60uF (10uF integer multiple), the recommended value is 50.00uF.
Note: The capacitor needs to adjust the above two points, directly output the corresponding range capacitor value, the program will automatically switch the range. "
----------------------------------

Note there is an 6/9V ACV high-frequency correction factor in EEPROM at 28H, 29H

Fungus:

--- Quote from: floobydust on September 07, 2017, 06:28:04 pm ---No serial data in/out. So not sure how data is being written to the EEPROM.

--- End quote ---

The same way it's read out on power-up...

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