DMM NEWACALOX DT33D

DSC_3264

This is a cheap DMM with manual ranges and a minimum of functions.

DSC_3229 DSC_3230 DSC_3231 DSC_3232

The box for the meters is without any brand name on it, but is designed for this series of meters.

DSC_3257

In the box was the meter, probe leads, a instruction sheet and a bag. The instruction sheet is for all four models in the series (A, B, C, D).

DSC_3261

The meter and the probes fits in the bag.

DSC_3262

The standard probes are a on the small side and made of a fairly hard plastic.

DSC_3263

The plugs are fully shrouded, but a bit shorter than standard probe plugs.

DSC_3267 DSC_3436

The tilting bale will only add a small angle to the meter and is stable enough to use the range switch and buttons. It is rather thin and will bend a bit when the range switch is used.

DSC_3265
DSC_3266
DSC_3268
DSC_3269




Display

DSC_3270
DSC_3271

Typical display during usage, it will show the number and HV when 500V range is selected. The hold button will turn on a H.



Functions

DSC_3274

Buttons: Rotary switch:

Input

DSC_3272


Measurements
squareOut

The square output is 50Hz with about 3.2Vpp

squareOut280k

The output impedance is around 280kOhm


DMMschema




Tear down

DSC_3439

I had to remove two screws, the battery cover also had to be removed to get the battery clips out.

DSC_3440

DSC_3442

DSC_3441

DSC_3443

To get the circuit board out I had to remove 4 screws. When this is done, the meter is rather tricky to put together again, due to the steel balls in the range switch.

DSC_3444

DSC_3445

And 3 more for the display (I removed one of them above).

DSC_3447

On this side of the circuit board is the range switch and two real switches for the buttons, there is also a backlight led.

DSC_3448

DSC_3449

DSC_3450

R10, R11, R12, R12A are the shunts for the uA and mA ranges. The transistors Q1 and Q2 is input protectiontogether with the PTC Rt1.
The resistors R1, R2, R3, R4 and R5 is the voltage input resistors (Nearly 10MOhm). The resistors R6, R7, R8, R9 is the input divider and D1 is the rectifier for the AC range.
The glass fuse is used for the uA and mA range, but not for ohm and V ranges. I am missing some diodes to protect the shunt resistors, this means they may be damaged before the fuse blows.

DSC_3451

DSC_3452 DSC_3454

DSC_3453




Conclusion

A unfused meter cannot have a CAT rating.
This is a fairlly simple meter with a minimum of ranges. It works fine and if the functions are enough it can be used, but unfused meters are best keept away from mains and from high current sources.



Notes

This meter exist with many different names on it and small variations in functions.
This meter looks like it is based on the UNI-T UT33D, but ranges are placed different on the switch and there is a battery lid.

How do I review a DMM
More DMM reviews