Instructions for the Sperry SP-5A

Preparation

1. Inspect the case of the SP-5A for cracks and other damage. Do not use the unit if it is damaged or extremely dirty.

2. Rotate the selector switch one complete turn and verify that it clicks into each of the 13 positions. Do not use the unit if the selector switch is loose or if it does not click into all of the positions.

3. Inspect the test leads for cracks in the insulation and broken, loose or bent probes. Do not use the unit if the insulation or probes are damaged.

4. Lay the unit on a flat surface. Turn the “zero adjust” screw with a screwdriver until it reads “0” on the left side of the scale.

5. Insert the black test lead into the negative terminal and the red test lead into the positive terminal of the unit. Do not use the unit if the test leads do not fit snugly into the terminals.

6. Flip the selector switch to the “X1K” position. Hold the tips of the black and red test leads together; make sure they touch. Turn the “OHMS” knob until it reads “0” on the OHMS scale on the right side of the unit. Replace the battery if a reading of “0” cannot be obtained.

Measure Voltage

1. Move the selector switch until it points to “AC” if you want to measure alternating current or “DC” if you want to measure direct current. Use the selector switch for the amount of voltage that is one step higher than the maximum voltage of the circuit you are going to measure. If the maximum voltage is higher than 500 Vac/dc, do not attempt to measure the voltage because the Sperry SP-5A is not designed to handle that amount of voltage.

2. Touch or insert the test leads to the two points of the circuit at which the voltage will be measured. Use the black lead for the negative point and the red lead for the positive point of the circuit when measuring DC voltage. When measuring AC voltage, the orientation of the leads does not matter.

3. Read the voltage measurement on the V-MA scale located below the mirror scale. Use the numbers that correspond to the voltage range selected. Use the red scale if the voltage range is 10 Vac.

Measure Current

1. Move the selector switch until it points at the mAdc range that is one step higher than the maximum current of the circuit you are measuring. Do not attempt to measure the current of a circuit if the maximum current is 250 mAdc or higher, or if you are unsure of the maximum current of the circuit.

2. Turn off the power to the circuit and discharge any capacitors or inductors.

3. Touch the red lead to the beginning of the circuit (the location where the power enters) and the black lead to the end of the circuit (the location where the power leaves).

4. Turn on the power to the circuit and recharge any capacitors or inductors.

5. Read the current measurement displayed on the V-MA scale. Use the numbers that correspond to the current range selected. Divide the 50 full numbers by 100 when using the .5 mAdc range to convert the numbers to an accurate reading.

6. Turn off the power to the circuit and discharge any capacitors or inductors. Disconnect the test leads, turn on the power to the circuit and recharge any capacitors or inductors.

Measure Resistance

1. Move the selector switch until it points to the “X1K” position.

2. Connect the test leads to the two points between which you want to measure the resistance. Do not measure the resistance of a live circuit; only measure the resistance of dead circuits with no power. The two points are where the power would be entering the circuit and where the power would be leaving the circuit.

3. Read the measurement on the top scale labeled with the Omega symbol, which resembles a horseshoe.

4. Multiply the reading by 1,000 to convert the numbers to an accurate reading.