Multi-function tester T7-H vs Mastech & ESR-micro v4.0 2022.04.06 at 16:43
And another article in English, just to be available for bigger audiences. Some time ago I received the Chinese multifunction tester T7-H, as it naturally understandable, without any proper documentation, thus decided to make a short test with it, comparing the capacitor measure function with ESR-micro V4.0. I’m not saying ESR-micro is in any way better, or I am advertising it, it just happened that I use it already for ~10 years and it works quite well.
First I will try to put all the information I found on the Internet, various sources, so I am not mentioning all of them, but if the information is copyrighted – I confirm its not my :), though I changed some of the information, to make ir properly readable. The manuals are written in Chinglish and some of technical characteristics are not even matching :D, tried to mark those discrepancies and put my comments for myself, to know what I should check during the test. The final result for me personally is to answer myself if I can trust the device performing well, because even if I saw several tests of the device – they all just go like „oh, look, it shows some digits”, but noone checks if those digits are correct.
128×128 TFT display
Multi function key
Transistor test area
Zener Diode test area
IR receiver window
Micro USB Charging Interface
Charge indicator LED
Features:
TC-T7-H is a TFT graphic display Multifunction Tester.
Transistor Tester:
Automatic detection of NPN and PNP bipolar transistors, N-channel and P-channel MOSFETs, JFETs, diodes (including double diodes), N- and P-IGBTs, resistors (including potentiometers), inductors, capacitors, thyristors, triacs and battery (0.1-4.5V) — oh, it can test battery ? Don’t forget to check :).
Automatic detection of zener diode(0.01-20V)
Self test with automatic calibration — how to start ?
IR decoder: — Cool, will have to test how it looks like.
Support Hitachi IR coding
IR waveform display
Infrared receiving instruction
Other:
Measurement results using TFT graphic display(160×128)
One key operation
Auto Power Off (Timeout Settable) — How to set ?
Built-in high capacity rechargeable Li-ion Battery — How high the capacity is ?
Li-ion Battery voltage detection — Is it the same as battery checking ? That seems a bit odd, why is then charged capacitor damages the device, whilst battery, when you think about it, could be considered as charged capacitor – don’t?
Support Chinese and English = Chinglish 😀
Performance Parameters:
Multifunction Tester can automatically identify elements and automatic detection of pin layout, and automatic switching range.
The main performance parameters are as follows:
| Component | Range | Parameter description |
|---|---|---|
| BJT | – | hFE(DC Current Gain), Ube(Base-Emitter Voltage), Ic(Collector Current), Iceo (Collector Cut-off Current (IB=0)), Ices (Collector short Current), Uf (Forward Voltage of protecting diode) ③ |
| Diode | Forward Voltage < 4.50V | Forward Voltage, Diode Capacitance, Ir (Reverse Current) ② |
| Double diodes | Forward Voltage < 4.50V | Forward Voltage |
| Zener diode | 0.01-4.50V (Transistor test area) | Forward Voltage, Reverse Voltage |
| Zener diode | 0.01-20V (Zener Diode test area) | Reverse Voltage |
| MOSFET | JFET | Cg (Gate Capacitance), Id (Drain Current) at Vgs (Gate to Source Threshold Voltag), Uf (Forward Voltage of protecting diode) ④ |
| MOSFET | IGBT | Id (Drain Current) at Vgs (Gate to Source Threshold Voltag), Uf (Forward Voltage of protecting diode) ④ |
| MOSFET | MOSFET | Vt (Gate to Source Threshold Voltag), Cg (Gate Capacitance), Rds (Drain to Source On Resistance), Uf (Forward Voltage of protecting diode) ④ |
| Thyristor | Igt (Gate trigger current )<6mA | Gate trigger voltage |
| Triac | Igt (Gate trigger current )<6mA | Gate trigger voltage |
| Capacitor | 25 pF – 100 mF | Capacitance, ESR (Equivalent Series Resistance), Vloss ① |
| Resistor | 0,01 Ω – 50 MΩ | Resistance |
| Inductor | 0,01 mH – 20 H | Inductance, DC Resistance ⑤ |
| Battery | 0,1 V – 4,5 V | Voltage, battery polarity |
①: Iceo, Ices, Uf displayed only when effective — „effective” here and below is probably a chinglish meaning for „available”
②: Diode Capacitance, Ir (Reverse Current) displayed only when effective
③: Displayed only when has protecting diode
④: ESR, Vloss displayed only when effective
⑤: Measurement of inductors with resistance below 2100 Ω
Operating instructions
Multifunction key has two actions:
Short press: Press the key for more than 10 ms and shorter than 1,5 seconds.
Long press: Press the key more than 1,5 seconds
Power ON
In the power off state, insert the part to be tested and short press the multifunction key, the tester is turned on and inserted part is automatically measured. Always be sure to discharge the capacitors before connecting them to the tester! The tester may be damaged before you have switched it on!
It is not recommended to measure the battery! The battery voltage must be less than 4,5 V, otherwise the tester may be damaged!
Those are the main things from the random sources, now lets look at the user manual. The user manual is for TC-V2.12k, which, I suppose, is also chinglish device and T7-H is its clone, or vice versa :D.
And now we know where are those mystical areas, mentioned in the first part of article. That is important, as measurement result in some cases will be different or would give more information. The display is clearly bigger, but lets forget about this for some time.
First function to be tried – automatic calibration. To start it just connect all 3 pins together (1+2+3) and short press the Start button. During the calibration the device will ask to remove the connection/jumper_what_ever_you_have_there and will finish calibration. My device performed this operation successfully.
It seems, that the firmware version is V2.12K. Is it just a coincidence that the same numbers and letters are in the name of device from user manual ?
Configurable thing – the power off time. Manual says, that it should be set to 20 s. To change the timing you should open the case and you will have the table with available settings:
I believe, timing is set using P1 and P2. Don’t know yet, what is P3 for. Enables pee free :D. Ok ok, the setting must be to set the language, 1 = ENglish, 0 = ChiNese.
For now I am not going through the firmware and its possible modifications, but will do the parts test. The battery is fully charged.
- Transistors
2N3903
BJT – correct
NPN – correct
hFE – incorrect, according to datasheet max 300. Could be due
to higher Ic or Vce.
Ube – correct, should be between 0,65 V and 0,95 V.
Ic – unable to confirm. In general – what is this Ic ? Manual says
collector current, but maybe its collector cutoff current?
BJT– correct
NPN – correct
hFE – could be correct (min 40, typ 80, max 250)
Ube – correct, judging from the datasheet, its somewhere between 0,6 V and 0,7 V
Ic – Strangely similar to 2N3903…
N channel MOS – correct
Vt – correct, according to datasheet at room temperature it could be about 1,5 V
Cg – Datasheet doesn’t mention gate capacitance, only gate charge…
Rds – incorrect, should be between 6,5 mΩ and 12 mΩ
Uf – probably correct.
BJT – well… It depends, its a Darlington pair of BJT’s
PNP – correct
hFE – incorrect, I would agree with value anywhere between 200 and 18000.
Ube – possible, max 4 V
Ic – Unable to confirm
Uf – Possible
N channel MOS – correct
Vt – correct, should be from 2 V to 4 V
Cg – Unable to confirm
Rds – incorrect, max 14 mΩ = 0,014 Ω
Uf – possible
BJT – I agree
NPN – Correct
hFE – Lets say correct, depends on measuring
Ube – Correct
Ic – doubtful value
BJT – Correct
PNP – Correct
hFE – Correct, should be from 50 to 100
Ube – Correct
Ic – doubtful value
Well, enough transistors. Bottom line – type and polarity of the transistors in most cases detected correctly. Has some issues with Darlington’s, maybe other, fancier, types of the transistors. There are some useless values, unless explained what do they mean. According to the manual, some of the measuring information is missing. In general, if you know how to measure transistors with tester/multimeter – device is not so much useful. Maybe makes it a little bit faster or if you need to check the parameters, which wouldn’t be so much accurate, but you’re OK with that.
2. Battery
I am not measuring batteries, maybe some day.
3. Diodes
1N4007, super popular rectifier
Uf – incorrect, Mastech MS8265 shows 0,5555 V
C – incorrect, should be 15 pF
Uf difference is ~20 %, C difference ~40 %, I cant even say its approximately accurate 😀
Uf – Mastech says 0,4265 V, still 20 % difference
C – datasheet says 85 pF, again about 40 % difference
Ir – should be about 10 µA, but at room temperature the graph is not so informative, so let say – probably Ok. Might be difference to measuring voltage value.
Uf – Masterch says 0,1673 V, so 30 % difference
Ir – datasheets says something about 2 mA, so not even close… But that might be to measuring voltage value.
Uf – Mastech says 0,3958 V, so 20 % difference
C – Possible
Ir – Not confirmed, but could be. Might be difference to measuring voltage value.
Had some big and powerful diodes, but I think its enough, to have an opinion… So the main diode parameter – voltage drop is not measured correctly, according to Mastech MS8265. The rest of parameters are not so much useful, unless at some specific designs, but people doing specific designs already knows what to look for.
4. Thyristor
Uf – Correct, should be min 0,4 V, typical 0,6 V, max 1 V
Have couple of those thyristors, second shows 755 mV, so the device actually measures something 🙂
5. Triac
Uf – Correct, typical 0,7 V
At this point can confirm, that thyristors and triacs are detected well.
6. Capacitor
To be finished 🙂 !!!
