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colsc 04/11/2018
The Mustool MT109 offers a lot for the price and delivers on the basics but does not live up to its full specifications in usage. !. The large clear display is great in shade and low light situations. Outdoors in sunlight the screen is almost unreadable. 2. The APO (Auto Power Off) feature should operate after 15minutes according to the manual. My meter turns off after 3 minutes. This cannot be varied although it can be turned off by button operation at the time of turning the operation switch. 3. The English language manual provided lacks detail on the use of button operations and is incorrect and contradictory in details of operation ranges. 4. The major shortcomings in the meter usage relates to the current measurement functions. (a) The advertised AC mA ranges do not agree with those in the manual -100/1000mA against 60/600mA in the manual although it states on the same page that the maximum current is 1Amp. (b) The manual agrees that the DC mA ranges are 100/1000mA with overload fuse protection of 1Amp.However when measuring approx. 800mA the fuse blew. On opening the meter the fuse was found to be rated at 0.63A and the printed circuit board specified a 600mA fuse. (This is the same fuse used for the AC mA operation). Replacing this fuse with a fast operating 1Amp fuse allowed display of the higher current but the internal buzzer beeped continuously whenever the current exceeded 600mA.This also happens with AC mA operations and is annoying. (c). The advertised specification of 10Amps is contradicted in the manual which in text below the 10A lists the AC/DC as 6A/10A and the maximum voltage drop as 600mV not the required 1A. In operation, any AC or DC current above 1A results in the continuous beeping buzzer although the correct value is displayed. (d). The manual says the maximum input current is 10A for not more than 10 seconds but the annoying beeping appears to indicate that a current in excess of 1Amp may need to be restricted to 10 seconds. 5. The buzzer operation is not mentioned in the manual and being quite loud virtually precludes meter operation in those current measurements. I also feel the loud sounding of the buzzer while turning the operating rotary switch is annoying and not necessary. SUMMARY- At the price this is an acceptable meter for anyone who is not relying on current measurements. The fuse replacement and labelling should be done by the manufacturer. This would be a step in the right direction but before I would recommend this meter to anyone the beeping buzzer notifications would need to be revised.
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colsc Themeter accuracy is within plus or minus 2% plus 3 counts of the least significant digit displayed. For example a 100 Volt source should read 100.0. With basic accuracy of 2% the reading would be anything between 98.0 and 102.0. This spread is further changed by 3 counts of the least significant displayed digit to allow display between 97.7 and 102.3 to be within specification.

2019-12-18 06:59:15 Helpful (1)
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