This is particularly true where voltage measurement is done in higher resistance circuit. It should also be noted that meter with higher sensitivity gives reliable result.
As shown in figure, R1 and R2 which are of 10k and 100k ohm. In the above diagram, A and B are the fixed ends/terminals and C is the variable terminal of the rheostat (a variable resistor).
#VOLT METER SERIES#
In this resistive network we have two resistors. Procedure for the Conversion of a Galvanometer into a Voltmeter: Connect the resistance box in a series combination across the galvanometer and then collect the plugs of resistance R. Voltage divider is a resistive circuit and is shown in figure. So in second case loading effect is not prominent as the voltmeter resistance is much higher than the circuit resistance but in first case loading effect id dominating as the voltmeter resistance is comparable to circuit resistance. Before entering into this Arduino Voltmeter circuit, lets discuss about the Voltage Divider Circuit. See how close to the true reading we get. Mind here that the resistance of voltmeter > circuit resistance i.e 1000 kOhm >50 kOhm so definitely we are going to get voltage reading close to true value i.e 50 V. This panel meter simply connects to whatever DC supply you are trying to track, easy to wire upSimply connect the red wire to the positive supply, and black to negative ground. Resistance of Voltmeter R VA= SensitivityxVoltage Adafruit Industries, Unique & fun DIY electronics and kits Panel Volt Meter - 4.5V to 30VDC : ID 575 - Put a voltage meter anywhere with this very handy display. Sensitivity of Voltmeter A = 20,000 ohm/V
It should be noted that for getting good accuracy, the resistance of voltmeter > circuit resistance but here in this case both are equal. Therefore we see that voltmeter A reads much less than the true value. Now when this voltmeter A is connected across the resistor of 50 kOhm, the equivalent resistance of the parallel combination, Circuit a: Voltmeter reads 1.5V, Ammeter reads 7.5A Circuit b: Voltmeter reads 7.5V, Ammeter read 1.5A Circuit a: Both batteries are in series so total valtage is 15V Circuit sries restnace is 2 ohms So Current I V/R 15/2 7.5A Voltage drop across top 1 ohm resistors IR7.5V, right side being +ve So Voltmeter reads +7.5 -6 V +1. Resistance of Voltmeter R VA = SensitivityxVoltage