Some time ago somebody (me) mixed SMD capacitors (the common unmarked multilayer ceramics) and a set of prototype boards was not working. I had to check the components value.
Time to buy a tweezers-type component tester, but budget was low, and the Smart Tweezers were out-of-reach.
I got this Lafayette DMB-SMB from one of my local distributors, at the very low price of 24 euros + VAT (list price is 34.13 euros + VAT)
http://www.marcucci.it/english/prodotti/schede/scheda.asp?ID=13876Actually the Lafayette brand (once a famous USA brand, specializing in C.B. radios) is used by it's former Italian distributor Marcucci for a lot of products, mostly OEM from China.
The same instrument is sold with the METRIX brand (model TCX-01 that was offered to me at 51 euros + VAT)
http://www.chauvin-arnoux.com/Produit/Famille_detail.asp?idFam=2112&idPole=1and I believe is the same that EXTECH sells as model RC 100 (not the RC 200 that nearly killed Dave on EEVblog episode 94)
http://www.extech.com/instruments/product.asp?catid=56&prodid=350 the AXIO model 103 and others you can find on the Net.
The instrument is boxed in a nice cardboard box, with Italian and English descriptions. and is supplied with an 3-page manual written only in Italian.
It can measure:
- resistance (auto-ranging from 400 ohm to 40 Mohm) with 0.1 ohm resolution on the lower range, and an accuracy of 1.2% plus-minus 3 digits)
- capacitance (auto-ranging from 4 nF to 200 uF) with 1 pF resolution on the lower range, and an accuracy of 3 % plus –minus 5 digits)
-diode voltage drop
Power comes from two 1.5 V button cells , type AG13.
Two buttons :
- FUNCtion to switch on/off and to change measurement function.
-RELative to change from absolute measurement mode to relative mode.
This function is totally un-documented, but I found that, by pressing the button when measuring a component, you shift the measurement zero by the actual value, setting the display to zero and subtracting the previous reading from the following readings.
That means: measure a 8k2 resistor, the display reads 08.20 kohm, pushing REL the display reads 00.00 koms, measure a 15k0 resistor, the display reads 06.80 koms (15.0 – 8.2). I don't see any utility in this, but it does not harm
The display is good quality, very readable. Character height is 13 mm.
I've tested the meter with various components, both soldered on the board and free on the bench top.
The auto-ranging speed is about 3 to 4 seconds for a stable reading, except for big capacitors, requiring a very long time for a stable measured value.
Measurements seemed accurate (I've not checked the accuracy).
Resistors were measured accurately and with the above speed both when naked and when soldered on the board.
Capacitors where measured accurately only when naked: capacitors on the board were difficult to measure, sometimes it was not possible to get a "credible" reading.
I must admit that I did not investigate too much… this was the first dislike.
The output voltage when measuring diodes is about 1.6 volts, insufficient for testing LEDs.
This was the second dislike.
The third dislike was the bigger one: the tweezers are too "rigid" and require too much effort for a reliable contact.
The tips are too large, a reliable contact with the component's pins is difficult to achieve.
When testing naked components, placed on the bench surface, many times the component was lost in the lab, "flying away" because of the bad tweezers tips (see photo at the end of the post) that launched it in the air.
The lack of a reliable contact made the actual use of the instrument very difficult, and very soon it went back into the box….
It's a pity, because the electronics are reasonably well made, and they work "not so badly", so when I'll find the time and some suitable material, I'll try to modify the tweezers into something similar to the "Smart Tweezers"design.
Taking apart the instrument is easy: remove the battery cover and the batteries, undo 4 self tapping screws, remove the back cover and you have access to the rear side of the circuit board. Notice: there are no input protections (or I did not find any).
The manual and the rear panel text clearly advise that the maximum input voltage is 50 V dc.
With some easy effort the PCB is released from the 4 latches that keep it in place, and the other side of the board is accessible. The display is connected to the PCB with "zebra strips". I did not remove it because, looking from the sides, I've seen that the only component under the display is the meter IC, but it’s a COB (chip on board), and there nothing of interesting in a "black blob"..
Summing things up: this meter is cheap (at 24 euro), the electronics are not-so-badly designed (but they should be improved), the mechanics are so lousy that actual use of the meter is really difficult. Thumbs down.