this double display meter has two sets of digital display, can measure and display DC voltage and DC current at the same time. 

This link is for the low-voltage version, i.e. the working voltage of the dual display meter itself is 4.5-30V. 100V10A means the voltage measurement range is 0-100V, the current measurement range is 0-10A. 100V50A and 100V100A and so on. 

this double display meter wiring is more complex, the wrong line can instantly cause damage, be sure to read the notes and wiring diagrams on this page in detail before purchase and installation.
 

Measuring range voltage: 0-100V, current 0-10A (or 0-504, 0-100A)
Minimum input: minimum voltage of DC4.5V for the dual display meter drive power supply
Maximum input: maximum voltage of DC30V for the dual display drive power supply
Allowable error: ≤1% "+/-1 word)
Display mode: two-way three-dimensional 0.28-inch LED digital tube display
Display colours: red+red, red+green, red+blue optional
Refresh speed: approx. 200mS/time
Current consumption: less than 25mA
Operating temperature: -10℃~65℃
 
Caution: 

1, this double display meter is suitable for the purchase and use of technical personnel with certain knowledge of electrical and electronic technology. 

2, the power supply voltage range for driving this double display meter is 4.5-30V, when the voltage of the tested circuit system meets this range, power can be taken directly from the tested circuit, the thin red wire and the thin black wire are the power connection wires; when the voltage of the tested circuit system is higher than 30V, this double display meter must be equipped with a special power adapter, the output voltage of the power adapter should meet the range of 4.5-30V, priority 5-20V is recommended.
 
3. 100V10A is a built-in shunt, 100V50A and 100V100A need to use an external shunt. For external shunt, before energising this double display meter, the connection between the double display meter and the shunt must be connected.
 
4. The current must be sampled from the low end. That is: the current of the circuit system under test flows through the load first and then through this meter (or the shunt connected to this meter). Otherwise, it will cause instant damage to this double display meter.
 
5, the concept of power supply and load of the system under test: when discharging, the battery, switching power supply, transformer, etc. to provide energy is the power supply; resistor, lamp, motor or other electrical appliances, etc. to consume energy is the load. When charging, the charger, generator, solar panel is the power supply, is charged all kinds of battery is the load.
 
6, this double display meter circuit board W1 is the measurement of voltage calibration trim, W2 is the measurement of current calibration trim. This double display meter has been precisely calibrated at the factory, please do not adjust it at will.
 
7, 100V50A and 100V100A double display meter, must be connected to the corresponding range of shunt to use, and to connect the shunt to power, otherwise it will cause instant damage to the double display. When connecting the shunt, the two large current lines should be fixed to the large screw of the shunt and the line connected to the double display meter should be connected to the small screw. Otherwise, it will cause great errors.
 
8, when connection or use problems, please refer to the following possibilities: a, no display or abnormal display: this double display meter needs DC drive power supply, please check whether this power supply is not filtered with large capacitors or the power supply ripple is too large; b, voltage display is normal, current display 0.00 or 0.0: circuit sampling connection error will cause this situation, please first return to Note No. 5 and refer to the wiring diagram to figure out The concept of power and load. Note that the same system, the concept of power and load is different when discharging and charging. c, the current display is not allowed: in the double display meter drive power ground and the ground of the system under test has been common ground, please disconnect the thin black wire. d, the measured voltage or current is zero, the double display meter display does not return to zero: first check whether the correct connection line, followed by checking whether the double display meter drive power ripple is too large, whether the sampling line is too long cause interference. Usually does not affect normal use when not zeroed. 

9.For 50A and 100A meters, no matter how much current is measured, an external shunt must be connected, otherwise the current cannot be measured.