DMM HoldPeak HP-770C

DSC_6309

This is a fairly cheap DMM with 40000 count display and lot of functions.

DSC_6282
DSC_6283
DSC_6284
DSC_6285

It arrived in a universal HoldPeak cardboard box.

DSC_6299
DSC_6300

Inside the box was a pouch with everything inside.

DSC_6301

It included the DMM, a pair of standard probes, a pair of alligator clips probes, a thermocoupler, a instructions sheets and the pouch.

DSC_6307
DSC_6308

No tip covers on these probes that is rated for 1000V Cat III and 20A
This means the rating is wrong.

DSC_7577

The plug is fully shrouded.

DSC_6304

The alligator clip probes are without shroud and fairly short because they are designed to be used with the LC test function.

DSC_6305
DSC_6306

The thermocoupler is encapsulated, this makes it useful for inserting in stuff, but not as good for measuring surface temperatures.

DSC_6312 DSC_6314
DSC_6313 DSC_6315

The tilting bale has multiple position, including one as a hanger.

DSC_6322

On a smooth surface the meter needs two hands to turn the range switch.

DSC_6316 DSC_6317

DSC_7586

DSC_6320

DSC_6321

DSC_7579

There is light in the range switch, it turns on together with the backlight.

DSC_7580

DSC_7581

DSC_7582

DSC_7583 DSC_7584

DSC_7585


DSC_7587

The metal ring on the back is a magnet, i.e. it is possible to attach the meter to metal surfaces.



Display

The meter do not show all display segments when turned on.

DSC_6324

Display during normal usage, it will show selected range and value.

DSC_7578

At the top is two leds used for the NCV, green when no field detected and red when a field is detected. The center position is a photosensor used to turn on the backlight on the display and the light in the range switch.



Functions

DSC_6325

Buttons: Rotary switch:

Input

DSC_6326

The capacity and inductance input connectors. The are used with 4mm banana plugs.

DSC_6327
The shutters secures mostly that only the correct inputs are accessible, the capacity and inductance are not covered by shutters.




Measurements 1uF

A look at the capacity measurement waveform when measuring 1uF.

10H

Here is the inductance measuring waveform, the frequency is about the same on all inductance ranges.

DMMInputVoltageSweepHz

Frequency input resistance.

DMMschema

When input voltage contains both AC and DC, the DC readout will be too low.






Tear down

DSC_7588

I had to remove two screws to open the DMM.

DSC_7589

DSC_7590

DSC_7591

DSC_7592

To remove the circuit board there was 6 more screws.

DSC_7606

DSC_7594

The shutter is controlled by a track on the range switch.

DSC_7598

This meter has a lot of chips, many of them are OpAmps: 2xLM358, TL062, TL072, a analog switch (4066), some Schmitt triggers / gates (7414, 4093) and a dual timer (4528).
The current shunts are near the 20A fuse (R10: 1ohm, R9: 9ohm, R8: 90ohm), there is two diodes to protect the current shunts (D7 & D8).
The 200kHz frequency range use the PTC and the transistor pair (T2 & T3) for protection, then the signal is going through a resistor and capacitor into the timer. This probably means that a analog voltage proportional to the frequency is generated and the meter measures that voltage to show frequency (Not very precise). Ohm output current is secured with the PTC and some transistors (T5, T6, T7). The voltage 10Mohm input is two resistors (R1 & R2: 2x4.5Mohm). The inductor measurement use some of the OpAmps and probably also the other chips.
There are many trimpots on the board to calibrate it.

DSC_7599

DSC_7601 DSC_7603

At the end of the circuit board is the NCV antenna, this an external part. There is 3 resistors (R77, R78, R79: 3x10Mohm) to maintain the potential on it.

DSC_7602

DSC_7596

I had to remove 5 screws more before I could remove the display.

DSC_7597

This side of the circuit board has the power switch and transistor tester socket and at the top two leds and a LDR to control the backlight. The sockets for the LC tester is also here.

DSC_7595

DSC_7605 DSC_7604




Conclusion

As usual on cheap(er) DMM's the CAT rating is wrong, meter cannot be rated for 1000V and use 500V fuses. The transistor tester may also be problematic and the LC tester is very problematic.
Looking at the range switch it might look like the meter has a lot of ranges, but it do not. The inductance range is seldom seen on a multimeter and here it is missing some low ranges to check the uH inductors used in modern switchers.
The shutters reduces the risk of mistakes when switching between voltage and current, it is a good safety feature, but the LC inputs are missing them.
To supported as many different measurements as possible the meter has skipped a lot of ranges, this means it is often possible to measure stuff, but with lower resolution.



Notes

How do I review a DMM
More DMM reviews