Three notable features for choosing a high-sensitivity multimeter
When conducting electronic measurements, choosing a high-sensitivity multimeter has the following three significant characteristics:
3. Easy to design high blocking. Because the voltage sensitivity is high, it means that the sensitivity of the meter head is high. A small test current can cause the pointer to deflect to full scale, achieving ohmic zeroing of the resistance range. Even in high impedance, lower battery voltage can be used.
Analyze the error when measuring voltage with a multimeter using the diagram below. Assuming the measured voltage is UV and its internal resistance is RV. The dashed box on the right side of Figure B is the equivalent circuit of the voltage range, with an internal resistance of RV and 0 indicating an indicator with zero internal resistance (the same below). Connect the multimeter in parallel in the circuit under test, assuming the multimeter reading is U1, there is a relationship equation
From the equation, it can be concluded that, rv＜0, Indicating that U1
1) When measuring a high internal resistance power supply voltage with two multimeters of the same range but different voltage sensitivities, the multimeter with high voltage sensitivity needs to be selected for measurement.
2) For the same multimeter, the higher the voltage range and internal resistance, the smaller the measurement error caused.
3) When the internal resistance of the voltage range is higher than the internal resistance of the tested power supply (more than 100 times), there is no need to consider the shunt effect from the tested power supply.
