13-07-2017, 09:12 PM
I've done a little bit more testing...
First, the -3dB point of these Aneng meters is 3kHz. That's not stella, but fair enough. The £280 Fluke 179 is similar, IIRC.
Next, the question about true-RMS. I would have been amazed if they'd have lied about that, given how easy it is to test. It's part of the IC, as mentioned earlier, and that IC is used in many other meters at higher price points than this.
However, it's easy enough to test (see attachment). I used my trusty old Wavetek 162 function generator, which can make a wide range of waveforms. My Fluke 8920A is as true-RMS as it gets, being a genuine thermal sensor. I also used my Fluke 87V, just in case. And while I was at it, I included the Bside ADM02, which isn't true-RMS, and gave the expected errors on non-sinusoidal waveforms.
In short, all 3 Aneng meters are indeed true-RMS. Even with very narrow pulses (hence high crest factor), the Aneng agreed with the 87V at all times. At the narrowest pulse widths, these two deviated slightly from the 8920A readings, but that's because it can cope with higher crest factors, of course.
Yes, that's because he tested at too high a frequency (see the YouTube comments), forgetting that the limited bandwidth will attenuate the harmonics and alter the results. For that reason I tested at 100Hz. There's a note in the manuals (except the AN8008, strangely) stating that frequencies above 200Hz won't be accurate. Of course, most multimeters have different tolerances for different frequency ranges - nothing unusual about this one.
The frequency readings rely on the input waveform crossing zero by an amount. This is not uncommon and is unlikely to be a big problem in practice, but the Fluke 87V doesn't have this problem. Stick a capacitor in series if needed!
I also discovered a minor "bug" with the AN8008. When measuring frequency on AC volts, you need a minimum of ~1.7V to get a reliable reading. The AN8002 works down to about 50mV, give or take (1kHz sine wave). Actually, if you use the yellow button to cycle back to AC, then press again to get Hz, you get do a reading for about 3 seconds, then it changes to zero. This works reliably down to about 100mV. I think what's happening here is the meter is changing to a higher range, rendering it less sensitive.
Using the dedicated Hz position is fine - the input sensitivity at 1kHz is about half a volt. That's not as good as the AN8002, which works down to about 20mV (as reported above, but has just been double-checked at 1kHz).
The two meters, despite their visual similarities, are obviously set up differently. The mV ranges are quite different (60mV and 600mV for the AN8002, 9.999mV and 99.99mV for the AN8008). Perhaps that explains the differences?
Either way, the frequency counter is still very usable, and as reported earlier, it has an astonishing response (out to at least 80MHz). The spec suggests 10MHz.
I've tested the current consumption of the AN8008 (I'm sure the other 2 are practically the same). It's just over 1.6mA in most modes, rising to 1.8mA in Ohms (2.7mA when probes are shorted), and falling to 1.2mA in Hz. With such a low current consumption, you wonder why they have an auto-off function! The backlight adds about 5.7mA to the current draw. With the leads shorted and the buzzer sounding in continuity mode, the draw is 15.4mA. The AAA batteries should enjoy a long life. The battery low warning comes on at 2.4 volts and the meter shuts down at 2.1V. During that time, the meter continued to measure 7.5V DC completely accurately. I noticed that if you pressed the yellow button, the meter came back on, showed the low-battery warning, and shut down again. Out of interest, I lowered the supply voltage, and found that it was able to keep doing this until 1.75V.
As suspected, the square wave output is very much dependent on battery voltage. In fact, the peak to peak amplitude is exactly the battery voltage. The rise/fall time is about 1us, and the waveform is free from overshoot and ringing. Because it's AC coupled, you'll get a reasonable amount of "tilt" when driving a load.
I'm sure there's plenty more I could test, but I remain highly impressed with these meters
First, the -3dB point of these Aneng meters is 3kHz. That's not stella, but fair enough. The £280 Fluke 179 is similar, IIRC.
Next, the question about true-RMS. I would have been amazed if they'd have lied about that, given how easy it is to test. It's part of the IC, as mentioned earlier, and that IC is used in many other meters at higher price points than this.
However, it's easy enough to test (see attachment). I used my trusty old Wavetek 162 function generator, which can make a wide range of waveforms. My Fluke 8920A is as true-RMS as it gets, being a genuine thermal sensor. I also used my Fluke 87V, just in case. And while I was at it, I included the Bside ADM02, which isn't true-RMS, and gave the expected errors on non-sinusoidal waveforms.
In short, all 3 Aneng meters are indeed true-RMS. Even with very narrow pulses (hence high crest factor), the Aneng agreed with the 87V at all times. At the narrowest pulse widths, these two deviated slightly from the 8920A readings, but that's because it can cope with higher crest factors, of course.
(13-07-2017, 07:55 PM)peter scott Wrote: This one is very tempting and appears to survive Joe Smith's abuse quite well but the true RMS may be suspect unless it's a one off faulty unit: https://www.youtube.com/watch?v=oNss6h0Zu98
Yes, that's because he tested at too high a frequency (see the YouTube comments), forgetting that the limited bandwidth will attenuate the harmonics and alter the results. For that reason I tested at 100Hz. There's a note in the manuals (except the AN8008, strangely) stating that frequencies above 200Hz won't be accurate. Of course, most multimeters have different tolerances for different frequency ranges - nothing unusual about this one.
The frequency readings rely on the input waveform crossing zero by an amount. This is not uncommon and is unlikely to be a big problem in practice, but the Fluke 87V doesn't have this problem. Stick a capacitor in series if needed!
I also discovered a minor "bug" with the AN8008. When measuring frequency on AC volts, you need a minimum of ~1.7V to get a reliable reading. The AN8002 works down to about 50mV, give or take (1kHz sine wave). Actually, if you use the yellow button to cycle back to AC, then press again to get Hz, you get do a reading for about 3 seconds, then it changes to zero. This works reliably down to about 100mV. I think what's happening here is the meter is changing to a higher range, rendering it less sensitive.
Using the dedicated Hz position is fine - the input sensitivity at 1kHz is about half a volt. That's not as good as the AN8002, which works down to about 20mV (as reported above, but has just been double-checked at 1kHz).
The two meters, despite their visual similarities, are obviously set up differently. The mV ranges are quite different (60mV and 600mV for the AN8002, 9.999mV and 99.99mV for the AN8008). Perhaps that explains the differences?
Either way, the frequency counter is still very usable, and as reported earlier, it has an astonishing response (out to at least 80MHz). The spec suggests 10MHz.
I've tested the current consumption of the AN8008 (I'm sure the other 2 are practically the same). It's just over 1.6mA in most modes, rising to 1.8mA in Ohms (2.7mA when probes are shorted), and falling to 1.2mA in Hz. With such a low current consumption, you wonder why they have an auto-off function! The backlight adds about 5.7mA to the current draw. With the leads shorted and the buzzer sounding in continuity mode, the draw is 15.4mA. The AAA batteries should enjoy a long life. The battery low warning comes on at 2.4 volts and the meter shuts down at 2.1V. During that time, the meter continued to measure 7.5V DC completely accurately. I noticed that if you pressed the yellow button, the meter came back on, showed the low-battery warning, and shut down again. Out of interest, I lowered the supply voltage, and found that it was able to keep doing this until 1.75V.
As suspected, the square wave output is very much dependent on battery voltage. In fact, the peak to peak amplitude is exactly the battery voltage. The rise/fall time is about 1us, and the waveform is free from overshoot and ringing. Because it's AC coupled, you'll get a reasonable amount of "tilt" when driving a load.
I'm sure there's plenty more I could test, but I remain highly impressed with these meters
