Vorläufig / Preliminary, work in progress
At https://www.banggood.com I have seen a low cost (12 EUR incl. shipping) DIY Inductance Capacitance Frequency Meter Tester Kit (ID: 1360199) with a processor STC89C52 and a housing (Acryl).
Unfortunately no documentation was offered.
It was delivered within 14 days, and now the search for the documentation started.
A kit with the name secohmmeter-capacitance-meter-inductance-meter-frequency-meter was offered from company saintsmart.com, and they had a link to the documentation (schematic, C source code).
All electronic parts are clearly labeled on the upper side of the PCB. But with a schematic it is a lot easier to understand.
A Video about the kit is also helpful, especially the comments.
A mouse click on a picture will increase to to a bigger size.
I will try following to improve the documentation.
Unfortunately the Inductor measurement does not work.
The accuracy is not specified.
- I did not found any explanation about the measuring principle.
It is better to buy the LC-Meter.
- Supply voltage: DC 5 V or DC 8-14 V or AC 7 to 10 V
- Board size: 6.8 * 8.5 cm
- Small capacitance measurement range: 1 pF - 2.2 μF (no polarity capacitor)
- Inductance measurement range: 0.1 μH - 1 H
- Frequency measurement range: 20 Hz - 400 KHz (measured small signal)
- Electrolytic capacitance measurement range: 0.5 μF--12000 μF (small / big switch)
- LCD display: 16 characters per line, 2 lines
- Accessories: Clip for 9 V battery
Accuracy: Not specified
See the picture above.
There a 4 x 2-pin screw terminals for the DUT (Device Under Test):
# from left to right Capacitors|Inductors|Frequency| polarized Capacitors IN GND IN GND
There are 6 push button toggle switches:
# from left to right Power ON Capacitors|Inductors|Frequency |big pol. C|small pol. C
Before you measure release all measuring switches. Only one switch at a time must be on.
- Current consumption: about 43 mA (inklusive LCD background illuminiation)
- CPU: STC 89C52RC, 80C51 Derivat
- Clock: 12.0 MHz
- LM393, Dual differencial Comparator
- Reference inductor: L1 100 uH, 0.6 Ohm
- Reference capacitor: C12 1.0 nF, C13 1.0 nF (replaced by 1% type)
- Power supply input could be either AC/DC because of D1 - D4
- R16 should be adjusted to 0.6321 x Vcc
- e.g. 5.096 V * 0.6321 = 3.221 V, measured at pin 5 of LM393
The housing is made well, with some exceptions:
The mounting of the PCB is done with 2 screws from the bottom side, see the picture on the right.
On the left side a cutout for the 10 pin programming plug for the CPU is missing. See the picture below on the left.
On the right side a 10 mm diameter hole is missing for the power supply plug. See the picture below on the right.
I left the front side off for 2 reasons:
Allow to easy access the battery.
Allow short pins for the test objects.
Capacitors: not measured yet.
Inductors: Measuring does not work!
If the zero point drifts, it will be shown if the C- or L-button if OFF and the mode was selected before.
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-- RudolfReuter 2018-11-13 18:03:21