This model consists of two d.c. ammeters and two d.c. voltmeters rated for making electrical measurements in general laboratory experiments. All the meters are accurate to within + 2% of full scale deflection.

Each ammeter consists of a scale, a range selector knob, two terminals a reset switch. The scale has two ranges: 0 to .5A and 0 to 2.5A. The range selector knob has 4 settings: .5A, 1A, 2.5A, and 5A. The two terminals are used for making connections to the meter. One terminal is red and is marked “+ and the other terminal is black and is marked “-”. The reset (push button) switch is used in case the ammeter is overloaded.

Each voltmeter consists of a scale, a toggle switch, and two terminals. The two terminals are the same as those of the ammeter. The toggle switch has two settings: 75V and 150V. The scale has two ranges: 0 to 75 volts and 0 to 150 volts.

D. C. METERS – MODEL DCVA – 100

D. C. METERS – MODEL DCVA – 100

 

CAUTION:

Take the following precautions BEFORE turning on the power to the circuit or device to which your meter is connected:

(a) Set the range knob to 5A, if an ammeter is to be used.

(b) Set the toggle switch to 150V, if a voltmeter is to be used.

(c) Connect your meter to the circuit or device.

MEASURING CURRENT:

1. Place the ammeter in series with the circuit or device. To do this, connect the most positive side of the line (side into which d.c. current flows) to the red terminal and the other side of the line to the black terminal.

2. Turn on the power to your circuit or device. If the needle moves off scale, TURN OFF THE POWER IMMEDIATELY. Seek the advice of your lab supervisor BEFORE YOU PROCEED. (As an exception, when motor current is measured, the needle may momentarily move off scale but then drops down within scale.

3. If the needle moves down scale when power is turned on, reverse your line connections turning off the power first. 4. With the power on, remember that you have selected the 5A setting on the range knob. Now multiply the reading on the .5A scale by 10. If the result is between 2.5 amps and 5 amps; then the result is the measured current. If the result is less than 2.5 amps turn the range knob to the 2.5A setting and read the current on the 2.5A scale. If the current is less than 1 amp, turn the range knob to the 1A setting then obtain the current by multiplying the reading on the .5A scale by 2. Proceed similarly if the current is less than .5A.

MEASURING VOLTAGE:

1. Place the voltmeter in parallel with the d.c. voltage to be measured. To do this, connect the positive point of the circuit or device voltage to the red terminal and the negative point to the black terminal of the voltmeter.

2. Turn on the circuit or device power. If the voltage is between 75V and 150V, read the 150V scale. If the reading is less than 150V, change the toggle switch to the 75V setting and then read the 75V scale.

3. If the scale pointer moves down scale when power is turned on, reverse the meter connections after you turn off the power to the meter.

WATTMETER – MODEL ACWM – 100

This model consists of two multirange wattmeters which can be used alone or together to measure the real power of a circuit or device in the latter case, of a balanced load. The wattmeter panel also has a chart.

Each wattmeter consists of a scale, a voltage and current selector knob, and 4 terminals. The scale ranges from 0 to 150 watts. The selector knob has two voltage settings: 150V and 300V; and an OFF position. In addition each voltage setting has three current settings: 8A, 4A, and 2A. Two of the 4 terminals are designated “AMPS” and the other two terminals are designated “volts”. The “AMPS” terminals are dark blue and orange and the two “VOLTS” terminals are light blue and yellow. These terminals represent the amps coil and volts coil respectively, of the wattmeter.

WATTMETER – MODEL ACWM – 100

WATTMETER – MODEL ACWM – 100