DMM East Tester ET3240

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This is a low end bench meter with interface for computer control.

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It arrives in a big very solid cardboard box with the DMM well protected inside.

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It includes the meter, a manual, a calibration certificate stating that the meter is in calibration, mains cable, a pair of probes with alligator clips and spare fuses.

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Standard probe, that looks like CATII types.

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The plug is fully shrouded.

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Isolated alligator clips to mount on the probes.

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The front has the display, the buttons and the input.

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The handle can be placed in many positions, but the locking is rather loose.

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On the bag is mains input with a fuse, a USB connector and the mA fuse.



Display

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The display uses a color LCD with a main value and a secondary display that is very well used to show secondary values selected with the blue buttons. Default secondary reading is percent of range or frequency for AC measurements.
The bottom of the screen is used to show the current settings, the blue buttons are NOT soft keys.

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Adjusting some settings for MAX+B and Limits mode.

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A four terminal ohm reading of a 100ohm 0.01% resistor.

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Statistic.



Functions

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On some buttons the SHIFT function are the top line on other it is the bottom line.



Input

The inputs are only CAT II 300V rated, i.e. the meter is not designed for industrial and service on electric installations.

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Measurements 1uF

A look at the capacitance measurement waveform.

2mA-20mA

Current auto range, there is a few ms where the burden voltage is due to the protection diodes, not the shunt resistors. It looks like there is some contact bounce on the relay.
From 20mA to 200mA the voltage drop is about 1.4V, but the time is shorter.

DMMschema

The meter has a slight issue in the high mA range, the input terminal is labeled 100mA, but the range is 240mA
High AC voltage can block DC readings.
AC voltage is 1Mohm input impedance.



Software

The meter includes a CD with software and manual, but that was a rather big disappointment.: There is one good detail with the implementation: it answers very fast, sampling at the fastest conversion speed is no problem.

I implemented the meter in TestController, here is some examples:

Mode

I support most modes in the meter

Setup

And some configuration, this is present for all modes with ranges.

Values

Getting the current reading from the meter and showing some statistic.

ReadOut

Large digit readout on the desktop.

Table

Collecting the data in a table.

VoltageCurve

Making a curve of the data.



Tear down

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To open it I had to remove two screws and pull the handle out.

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Most of the meter is on a single circuit board. There is a IO board at the back. The main input goes to the circuit board where the switch is mounted and then back to the transformer. There is a isolation slot between the mains part and the rest of the circuit (nice).
The mA fuse is connected to the circuit board with wires and a connector.

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There is no parts on this side of the circuit board.

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A closeup of the backside of the circuit board. two budge wires can be seen.

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The IO port only have the USB connector mounted. These is also space for a RS232 output with a driver chip and for trigger and square wave connectors.

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The front side circuit board. The flat cable is for USB connector, it is handled here. It also looks like the trigger and square wave may be controlled from this processor.

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The power supply part of the circuit board. It looks like +/- 5V (U20 & U22: 7805 & 7809) and a more powerful 5V (U21: 7805) with heatsink.
Next is a isolated switching supply for the front panel, it also has opto isolated connections to the main board

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This part is the electronic range switch, a large part of it is done with relays. There is a big red input capacitor for the AC ranges.
There is four diodes (D13..D16) that handles overload on mA ranges and limits the voltage drop when changing current range.

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The 12A range has a fuse, but it is soldered into a isolated holder.

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Conclusion

The meter measures nicely, but the user interface is not completely logical, sometimes a specific function can be a bit hard to locate.
The computer interface is lagging documentation and software, I got the documentation from Banggood and the last bit can be solved nicely with my software.

Generally it works fine as a low end bench meter and I prefer it over the bench meters that are basically a handheld meter in a large enclose with a power supply.



Notes

Download TestController from here

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