Review on Amprobe PRM 6 Sequence Rotation Tester by Robert Pierce

Just a word of warning, I'm an electrical engineer. I have a standard Fluke 87V workhorse on my desktop and I really like it. However, it is quite expensive. My cheap $35 RS-DMM for home electrician hobby and odd jobs finally broke after 16 years. So I wanted to buy a fairly good quality gauge that didn't cost as much as the Flukes. I probably spent about 8 hours at times going through various DMM specs, user guides, and product reviews to find one that had all the features I wanted, had pretty decent accuracy, and was well made too. last. My price range was $50 to $70. However, I could not find one in this price range that meets all these criteria. The Extech 400 and 500 kept popping up, but reviews found some real quirks that we didn't like (poor fuse placement, button operation was intermittent, etc.). As I increased the price range, I found this Amprobe AM-570 DMM. Overall, I'm impressed with the overall quality of the meter. Good quality molded rubber. The grip feeling is good. After disassembling the gauge I was impressed with the quality of the PCB design. (I read that some gauges were pretty bad in build and solder quality). Overall, I really like this gauge. However, there were two REALLY BIG ISSUES that immediately caught my eye. Input terminals and NCV function. INPUT CLAMPS! It was EXTREMELY difficult to insert the probe into the V+ input jack, like something was blocking it. After 20 uses it got a little better. So I think this terminal will eventually be fine. The COM input port looked more like it should be (e.g. Fluke 87V). However, the input terminals A and mA cause most of the complaints. Leads slide well in them, but their holding power is extremely low. They don't have to be loose, there is minimal effort to hold them. It seems that when the wire is inserted, the distance from initial contact to final landing is only about 1.7mm. If you insert the probe cable into the A or mA input port, tilt the meter to the ground, let the cable hang, and even shake the meter slightly, the cable will come out in 2-3 seconds. If you disassemble the meter, you will see that the V+ and COM terminals are arranged differently than the A and mA inputs. The A and mA inputs are each held onto the wire by just two side bent contacts. Looking at the entry of these terminals with the case removed, the probe will actually go about 1.7mm past these bent pins before stopping. I'm not sure why Amprobe made these terminals so loose, perhaps as a result of implementing a "Warn about incorrect input terminals" feature. If you are an Amprobe seller reading this review PLEASE SOLVE THIS PROBLEM as this is a HUGE black spot on an OTHERWISE GREAT gauge. The only reason I'm not returning it for this reason is that I took the block apart and saw that there is at least a good electrical connection between the input terminals and the probes. Also, when taking current measurements, there were no intermittent readings when I wiggled the wire connection until I pulled the wire out 1.7mm. I've never used the NCV function on a gauge, so I'm not sure if there's a proper way to use it. But I'm pretty sure NCV FUNCTION is NOT on this gauge. By placing the top of the meter (where the light is) it may register the voltage at the 115V AC outlet 1 in 8 times and then only intermittently. It didn't go any better with a 220VAC socket either. I've tried touching the meter (where the loop of velcro is) right on the socket, rotating the meter and also moving the top to see if the sensor is in a specific spot. But nothing helped. The only time it worked well was when it worked with the power cord plugged in. Then it worked 100% of the time with a response time of 0.25s. So if the NCV function is only for new installations with the drywall removed and the electrical wiring exposed, this function works great. But when you use it in outlets, it doesn't work well. It wasn't a deal breaker for me as I wouldn't be using it much anyway. I can always use probes. After purchasing this AM-570 I took it to work and did some comparison measurements with the Fluke 87V. Running these tests with these two gauges side by side, I was very impressed with the accuracy, response time and functionality of the AM-570. Of course, the Fluke 87V has its own ± tolerances and is not really intended to be used as a measurement standard. But overall it has tighter tolerances than the AM-570. I also used an Agilent 33210A function generator for frequency and duty cycle testing. So the measurements of Vdc, Vac, Idc, Resistance, Diode/Continuity, Capacitance, Frequency and Duty Cycle appeared to match the published AM-570 specifications. There were a few measurements that seemed slightly out of spec, but they could be due to the Fluke 87V measuring at one end of tolerance and the AM-570 at the other. I could not compare the temperature values. Some of the specs I measured that I was looking forward to but not on the datasheet were: Frequency measurement sensitivity (measured with sine wave input): Frequency range > Sensitivity: 60Hz > 150mVp-p. 600Hz > 150mVp-p. 6kHz > 150mVp-p. 60kHz > 170mVp-p. 600kHz > 200-400mVp-p. 6.0MHz > 400-500mVp-p. 10MHz > 600mVp-p. Unfortunately, the function generator only increased to 10 MHz. Duty Cycle Sensitivity (for ±2% error): 4 Hz to 3 kHz > 400 mVp-p 3 kHz to 10 kHz > 400 mV to 1.5 Vp-p 10 kHz to 60 kHz > 1.5 to 2.2 Vp-p 60 kHz to 600 kHz > 2.2 to 3.9 Vp-p 600 kHz to 1 MHz > 3.9 to 5.0 Vp-p The error started to be > 2% above 1 MHz. Unfortunately, the duty cycle of the function generator was in the 20% to 80% range. So I couldn't test the entire AM-570 range. Response Time: - Vdc: Auto: 0.5s Manual: 0.25s - Vacuum: Auto: 1.0s (1.5s to stabilize). Manual: Approximately the same - Idc (10A): 0.25 sec - Idc (mA): Auto: 0.5 sec Manual: 0.25 sec - Iac (10A): not tested - Iac (mA): automatic and manual: 1 sec (2 sec to stabilize) - Resistance (until the reading stabilizes): automatic and manual: from 1 to 3 sec (depending on the value) - The analogue scale is very fast (20/s) and is useful for picking up faster through signals. Overall, I really like this meter. This is a great meter for the more serious hobbyist, and probably most professional test benches too (as long as you don't mind a little longer response time and as long as you don't mind current probes). It will probably also work for field use if you don't use it for current measurements (with lines out). I could see how this would be very helpful to the HVAC guys. Here are the pros and cons I found: Pros: - Quality designed and built. Good casting work. Nice solid body and handle. The buttons have good tactile feedback. The water resistance is good. Lies comfortably in the hand. I really like the texture of the side handle. It's really easy to hold in your hand, the chances of it slipping out of your hands are minimal. The response time is sufficient for most applications. There were some comments that the response was slow. But I think it's useful for most applications. Switching to manual range gives you faster response times when you need them. In addition, after the measurement has started, the display is updated 3 times per second for further reading changes - In Vac and Iac mode, the frequency is also displayed in the upper corner - The analog scale is fast and the graduations are fairly accurate. .- Has min/max functions.- The flash will definitely come in handy when doing electrical work. The light is a single high brightness white LED. Not super bright, but bright enough to see what you're doing in the dark. Stays on for up to 15 minutes. - Automatic switch off after 15 minutes. My last meter annoyed me endlessly with an automatic switch-off after about 2 minutes. - The backlight stays on indefinitely until the meter turns off after 15 minutes. - Two temperature sensors. You can see how handy this would be for HVAC.- The back stand is wide so the meter doesn't fall off as easily as other meters. Stands at a good angle - Probe holders on the back of the case hold the probes securely - Battery is easy to change. The battery cover is separate from the rest of the case. The battery cover screw has a metal machine thread. - Decent Cordura pouch that will fit all the items that come with the meter. - Pushbuttons are supplied with safety tips (less exposed metal areas). - The fuses are easily accessible after dismantling the case and are clearly marked so replacements should be fairly easy to find - Manual supplied on mini CD. It's very useful, especially with specs. Cons: - TOO LOOSE wires to A/mA input terminals. - Bad NCV function. - Response to resistance may be slightly faster. But I don't mind much. The response time of the continuity function could be a little faster. The min/max function places the counter in the manual range, resulting in the declared minimum and maximum values only within that range. So if a temporary minimum or maximum falls outside of this range, it will only show as "OL”. These modes do not display frequency and duty cycle at the same time. Overall I would give this DMM a 3.5 out of 5.