Answer:To design a parallel multi-range DC voltmeter, we can use the PMMC meter movement along with a series of resistors, as shown in the circuit diagram below:
R1
--- R2
Vinput ----+--|___|----+--|___|----+--|___|----+--|___|----> Voutput
| | | |
R1+R2 R3+R4 R5+R6 R7+R8
In this circuit, the PMMC meter movement is connected in parallel with a series of resistors (R1 to R8). The resistors are switched based on the input voltage, allowing the meter to measure a range of voltages.
To calculate the values of the resistors, we can use the following formula:
R = (Vout / IM) - Rm
where R is the value of the resistor, Vout is the output voltage, IM is the full-scale deflection current of the meter, and Rm is the resistance of the meter.
In this case, we want to design a voltmeter with ranges of 1 V, 10 V, 25 V, and 75 V. Let's calculate the values of the resistors for each range.
For a range of 1 V, let's assume that the full-scale deflection current is 100 µA. Using the formula above, the values of R1 and R2 can be calculated as:
R1 = (1 / 100e-6) - 22 = 9.78 kΩ R2 = (1 / 100e-6) - 22 = 9.78 kΩ
For a range of 10 V, let's assume that the full-scale deflection current is 10 mA. Using the formula above, the values of R3 and R4 can be calculated as:
R3 = (10 / 10e-3) - 22 = 978 Ω R4 = (10 / 10e-3) - 22 = 978 Ω
For a range of 25 V, let's assume that the full-scale deflection current is 10 mA. Using the formula above, the values of R5 and R
Step-by-step explanation: