In the next article devoted to the gadget that has a chance to appear in the Elektrody shop, I would like to present you a very small and handy multimeter (or actually a "multimeter") of Chinese production (of course, of course).
For the price of about five dollars, we can buy a very cheap and tiny "gauge". Although this "toy, together with the 6F22 battery (which is not included), weighs more or less as much as the battery, to my surprise it is quite a functional multimeter. However, for less than PLN 20 with shipping, there is nothing to complain about. it even had boxes, was wrapped in shrink wrap and wrapped in bubble wrap. The set also includes "test leads". However, their quality leaves much to be desired. So I used my own.
Below, I present a dozen or so photos showing the comparison of measurements with the "meter" that I use every day. It is impossible to disagree with the facts. This little Chinese "cockroach" looks perfectly correct as far as the measurement results are concerned.
On the above photos you can clearly see how tiny this "multimeter" is. Unfortunately, the thickness is close to "standard" multimeters. You can also see that it has a screen backlight. However, once it is turned on, it cannot be turned off. You have to set the selector knob to OFF, thus turning off the entire device. When turned on again, the backlight will be off by default. There is also a HOLD button that allows you to "freeze" the result of the current measurement.
The photos at the top show a comparison of DC voltage measurements ranging from five to thirty volts. My power supply doesn't really give the full 30V, but we can skip that.
Here (above) we can see the current measurement (interestingly, the meter "can" measure only direct current),. As you know, ammeters should not be connected in parallel or in series (and here you have a chance to prove yourself and write why). Therefore, the measurement is performed alternately on both multimeters. On the same test leads. A 12V 21W car bulb was used as the load. The supply voltage in the first case was 12V, and 5V in the second.
Alright. DC voltage, it measures quite correctly. So let's see how this little one deals with AC. In the pictures above I have recorded a comparison of measurements in the range of 12VAC to 285VAC.
Now it's time to test the ohmmeter:
As you can see in the photos above and below, when measuring resistance, the results are perfectly acceptable. Especially since, as you probably noticed, the measurements (due to my laziness) were made on two different resistors from the same package. And we know that even in one "strip" of 100 pieces, they will be different.
I have not tested the HFE measurement of transistors, because although I have this function in all my multimeters, I have never used them in my professional or amateur career.
I forgot one more important thing. I scanned the user manual for you.
Summarizing. It is quite a useful tool (apart from the tragic quality of test leads). If it appears in the electrode shop, it will certainly be useful to many young electronics enthusiasts. And even if someone spends the $ 5 and buys them on their own, and then "measures", for example, the resistance in a 230V socket, it will not be a regret.
Best regards. CMS
EDIT: 2018-07-26 16:53
At the user's request, I add photos from the center of the multimeter.
Please pics from inside.
As you suspected, we will not find out what integrated circuit the meter is built on, because we only have a "black dot".
Echhh, 5 baksów - in 93, probably, when I bought the first digital multimeter, the successor of the C4353 (hallelujah, no longer needed a calculator!) I paid almost 700,000 for it. PLN - the teacher then earned approximately 5 million. PLN.
The author compared rather two unknown integrated circuits - possibly - the same type - inside these devices - one probably in a large standard housing and the other in the form of a plastic drop on the electronic circuit.
I am waiting for reviews of a decent multimeter at an affordable price. Yes, in the range of PLN 200-300
I have a Sanwa RD701, indication up to 4000, measurement of frequency, capacity, temperature, true rms, nice meter. Possibly newer CD771 / CD772 but somehow I'm not convinced by their appearance.
It is also worth taking an interest in Aneng AN8009, for about PLN 70 we get an indication of up to 10,000 and power from two AAA sticks. It's not as well made and doesn't have as good security as sanwa but as a second meter or pocket / portable it's great, especially the resolution of the measurements is tempting.
affordable multimeter. Yes, in the range of PLN 200-300
UT136 good price / quality ratio (automat, backlight). UT61E (resolution 22'000) of course automatic, TrueRMS, unfortunately there is no backlight. Protection on everything 600V, fuses in ranges 1 and 10A. UT203 - Clamp, cheap (PLN 140) and also measures direct current, resolution 4'000.
Added after 1 [minutes]:
Today I will describe another small meter with True RMS and 6000 resolution
At 3 measurements per second, maybe it has a resolution of 60'000? I mean DT-987 (PLN 300 net).
For me, I always have two meters on the table: the first is the Fluke 289, and the second is the Mastech M-830B, but the latter is most often used because it costs pennies. In addition, I also have a drawer similar to the M-830. @CMS your advertised product will be a nice alternative for some of us and a nice device for beginners.
almost identical meters could be bought in supermarkets. The record I saw is 9.99 PLN. The only thing that did not have the backlight. Currently, you can buy it in DIY stores, recently similar, probably after 16.99 or 19.99. Personally, I would see other things in the shop, not necessarily such a meter. Let there be something I can't buy from the shop around the corner.
But you will not correctly measure the current flowing in the circuit you are going to check it.
OKAY. With serial connection of ammeters the result will be low, but by how many percent?
As you know, ammeters should not be connected in parallel or in series (and here you have a chance to prove yourself and write why). Therefore, the measurement is performed alternately on both multimeters. On the same test leads.
If we only want to compare the indications of both meters, the serial connection is correct and even necessary when the current source and receiver are not stable.
But you will not correctly measure the current flowing in the circuit you are going to check it.
OKAY. With a parallel connection of ammeters, the result will be low, but by how many percent?
As for the measurement error with one ammeter and two in series, it depends on the shunt resistance. It is therefore advisable to perform the measurement on a high measuring range. Unfortunately, the indicator error will increase the more the lower the value indicates. The accuracy of the meters is given for the maximum indication (most popular meters 1999). For 199 the error is bigger, for 19 it is huge, especially when you take into account +/- 2 or more digits. Once upon a time at EdW it was made clear.
Let's see how the cheap DT830D digital meter is useful for measuring mains voltage. Such a meter can be purchased for about PLN 10 (the box itself is probably worth more). DT830D is equipped with a 3 1/2-digit display, and the most suitable measurement range for us is 750 V with a resolution of 1 V. The measurement error is +- (1.2% + 10), which for a measured voltage of 230 V will result in a spread of values in the range of +- 12.76 ?13 V, that is from 217 to 243 V. Well. Epic fail. This "meter" (quotation marks probably justified, because in this case the device should be treated rather only as a voltage indicator) "does not even reach the heels" of an analog and quite average UM-ce.
As for the measurement error with one ammeter and two in series, it depends on the shunt resistance.
I know as much (and the rest) of what you wrote, but I was hoping that the opponents of serial connection of ammeters would estimate this error, because I do not undertake the task due to the heat. Let's take the simplest example - analog milliammeter without shunt, range 0-100mA. We have two such meters that measure without errors, i.e. measurement error = 0%. Both meters, connected to the circuit individually, measured 90 mA. What amperage will each meter show if we connect them in series? What error will cause serial connection of ammeters? Let us assume that the internal resistance of a milliammeter is 1 ?.
Mostly microammeters are used and a shunt is needed for the 100mA range. Let's say this is a milliammeter. For calculations, it is necessary to know its sensitivity (resistance). The wire in the body can be thick and have low resistance or thin and high.
The topic, however, is about digital meters. Popular designs are based on ICL7106 mutations measuring in the 200mV range. Here, the welding is simple, for 100mA it will be 1R. 100mA at 1V will cause a voltage drop of 100mV. However, when the meter has a resolution of 20'000, the reference voltage is not 200mV but 2V. So the shunt resistance will be 10R. It's not a good thing, so it will probably be a 1R and a x10 amp. Less frequently, the reference voltage will be reduced to 200mV. Manufacturers recommend a specific voltage to achieve high accuracy. Following this, a meter on the ICL7106 with a 200mV reference voltage can have a 0.1R shunt and a x10 amplifier or a 100mV reference voltage and a 0.5R shunt.
A beautiful argument, but my friend still did not answer the question I asked - how much will the indication of the milliammeter decrease if we connect two identical milliammeters in series. Since they are identical, it does not matter whether they both have identical shunts or not. Deriving the formula is very simple. A colleague may give this formula or make calculations for the assumption I have made; Rw of the meter = 1?
The topic, however, is about digital meters
Yes, but a colleague CMS he asked a general question about all types of ammeters
As you know, ammeters should not be connected either in parallel or in series (and here you have a chance to prove yourself and write why) .
The topic is yes, but my colleague CMS asked a general question about all types of ammeters
I will specify it, because although I have an analog multimeter and I use it occasionally, where digital (even with a bargraph) cannot do it, when I asked you this question, I meant only digital "meters". We also omit the issue of the wire used in the system and other nuances related to analog devices)
Gentlemen, did any of you notice how the current in the circuit affects the connection of such a multimeter?
Of course I did. Since no one is eager to derive the formula, I will suggest: It affects the less the greater the difference between the circuit resistance Ro and the internal resistance of the connected ammeter Rw assuming that the source powering the circuit is rigid. For Ro = 1000 Rw, the change of the measured current is approx. 0.1%, for Ro = 100 Rw approx. 1%.
when I asked you this question, I meant only digital "meters".
OK, but how the serial connection of ammeters affects the current measurement depends only on their internal resistances. It doesn't matter if one is digital and the other is analog or both are of the same type.