DMM BSide ZT301



This is a cheap DMM with all common function.



The meter arrived in a fairly anonymous multimeter box, but the checked illustration on the back matches the meter.



It included the DMM, a pair of probes, a thermocoupler and a manual.




The probes has removable tip covers, but is only rated for CAT-II, even with the covers on.



The plug is fully shrouded, but is slightly smaller than standard probe plug size.




A standard cheap termocoupler.



When using the tilting bale the meter is nearly stable enough to turn the switch, but the meter is very smooth and will easily slide around.












Display



The above picture shows all the segments on the display.



Typical display during usage, it will show the number and what measurement is selected.
The current software version has a bug, in manual ranging the manual annotation will disappear when using the range button.


Functions



Buttons:

• Range: Will disable auto range and change range, hold down to activate auto range.
• Rel: Shows values relative to current value, will also select manual range. Press again to disable.
• Max/min: Starts recording maximum and minimum value (This mode will also select manual range), press to select between max/min.
• Hz %: Shows frequency and duty cycle in AC voltage and current ranges and Hz range.
• Hold (Blue): Freezes the display, hold down for backlight.
• Select (Yellow): Select the ranges printed with.

Rotary switch:

• Off: Meter is turned off
• V: Show DC or AC voltage, using the HZ button to select frequency and duty cycle in AC.
• mV: Show DC or AC mV.
• : Resistance, continuity, diode and capacitance.
• Hz %: Measure frequency and duty cycle (Use the Hz % button to select).
• A: High current range for AC and DC.
• mA: Medium current range for AC and DC.
• uA: Low current range for AC and DC.
• °C °F: Temperature.

Input

• 10A mA: High current, it is not stable when current gets near 10A
• uA: The lower current ranges.
• CON: The common terminal for all ranges.
• xxx: All other ranges.

Standard probes cannot be fully seated in the terminals, but they will make contact. Banana plugs fits perfectly.



Measurements

• Volt and frequency
  • At 100mVrms frequency input range is from 1Hz to 5.1MHz
  • At 1Vrms frequency input range can be stretched to 7.3MHz
  • At 2Vrms frequency input range can be stretched to 70MHz
  • Max/min needs about 380ms to capture a voltage, it cannot capture on a single pulse.
  • 1 VAC is 5% down at 2.1kHz (RMS will not work at this frequency).
  • Frequency counter and duty cycle needs a zero crossing
  • Duty cycle works from 2% to above 99% at 100kHz with 1Vpp, precision is within 0.2 (Mostly 0.1).
  • Input impedance is 10-11Mohm on DC and AC
  • mV range is high impedance for DC and 10Mohm for AC, impedance drops above 1.8V to 3kohm
  • Frequency input is 10Mohm up to about 1.5V, then it drops to 2kOhm
  • Voltage input are rated for 100VDC and 750VAC, but mV input only for 0.8VAC/DC
• Current
  • A range will give audible alarm at 10A.
  • uA range will give audible alarm at 6mA, but works up to 8mA
  • mA range will give audible alarm at 600mA, but works up to 800mA
  • A range cannot handle near 10A, shunt will heat up and reading will change.
  • uAmA protected by a 0.8A/250V 5x20mm fuse
  • A is protected a 10A/250V 5x20mm fuse.
  • Current ranges are only rated for 36VDC and 25VAC
• Ohm, Continuity, diode and capacitance
  • Ohm needs about 2.7s to measure 100ohm
  • Ohm is 1.0V open and 0.4mA shorted
  • Continuity is (about 20ms).
  • Continuity beeps when resistance is below 50ohm.
  • Continuity is 1.0V open and 0.4mA shorted
  • Diode range uses 3.2V, max. display is 3.0V at 0.12mA, max. current is 1.8mA shorted
  • 10uF takes about 4.2 seconds to measure.
  • 70000uF takes about 10 seconds to measure.
  • The specifications says not to input voltage in these ranges.
• Miscellaneous
  • Current consumption of meter is 1.5mA and 1.9mA in AC mode (9mA with backlight).
  • Meter works down to 2.2V where it turns off, battery symbol show at 2.4V.
  • Reading is stable with changing battery voltage.
  • Backlight only works down to about 2.6V where it is fairly dim.
  • The meter usual need a few display update to reach the final value.
  • Viewing angle is good.
  • Display updates around 3 times/sec
  • Backlight will automatic turn off in about 140 seconds.
  • Will automatic turn power off in about 15 minutes.
  • Standard probes cannot be pushed fully down.
  • Weight is 248g without accessories, but with batteries.
  • Size is 161 x 80 x 40mm.
• Probes
  • Probe resistance 56mOhm for one (One probe was defective).
  • Probe wire is soft and 65cm long.

A look at the capacitance measurement waveform.



Frequency input impedance.



The 10A range is not stable near full current, it drift 2% in 15 seconds.
There is not much sound from the buzzer.



Tear down



Four screws and the back could be removed. The missing part of the enclosure is not something I have done, but was present in the meter.





As usual the circuit board is made to fit the enclosure.





I had to remove 3 more screws and loosen two clips before I could take the circuit board out.







To removed the display I had to remove two more screws and two clips.



The uAmA current input uses the two resistors next to the 10A fuse (R23, R24: 99ohm, 1ohm) with the protection diode next to the 0.8A fuse (D5: 6V8). The voltage input has 3 paths, one for voltage (R29, R30: 2x5Mohm), one for ohm drive (PTC1) and one for sense ohm, Hz, temperature (R25: 900k). The PTC has a transistor pair for extra protection (Q3, Q4), for the other inputs it must be handled by the DMM chip.
Next to the DMM chip is a EEPROM (IC1: 24C02A).









On this side is only the pads for the LCD and the switches.





Conclusion

As usual I am very doubtful about the CAT rating, it must survive full voltage on the ampere input, but they are not rated for that, neither are the fuses.
The meter has many ranges and some functions (REL, min/max), but are missing some of the more advanced functions.
The meter can do min/max, test leads and the backlight do not turns off after 15 seconds.

It will call it fairly good DMM for hobby use, but keep it away from anything with mains voltage and lots of amps.



Notes

This meter exist with many different names on it and small variations in functions.
Check the Aneng AN8008 meter for a smaller version of this meter.

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