🔌 Using a Voltmeter

Essential guide for testing electrical systems in parking and access control equipment.

⚠️ Safety First

Always use insulated test leads and probes
Wear appropriate PPE (safety glasses, insulated gloves)
Never test energized circuits above your skill level
Assume all circuits are live until proven otherwise
Keep one hand in pocket when testing to prevent shock path through chest

Meter Setup

Inspect meter: Check for damage to leads, probes, or meter body
Test meter: Verify function on known voltage source first
Select correct setting: AC voltage (∼V) or DC voltage (V⎓)
Select range: Start with highest range, work down

Testing AC Voltage (120V/240V)

Set meter to AC voltage (∼V)
Select 200V or 600V range
Connect black lead to COM (common/ground)
Touch black probe to ground or neutral
Touch red probe to hot conductor
Read voltage on display

💡 Tip: AC voltage in USA should read 110-125V for 120V circuits, 220-250V for 240V circuits.

Testing DC Voltage (12V/24V)

Set meter to DC voltage (V⎓)
Select appropriate range (usually 20V or 200V)
Connect black lead to negative terminal or ground
Connect red lead to positive terminal
Read voltage (watch polarity - negative reading means leads reversed)

Common Parking System Voltages

Equipment	Voltage	Type
Gate Controllers	24V or 120V	DC or AC
Loop Detectors	12-24V	DC
Barrier Operators	120V	AC
LPR Cameras	12V DC, 24V AC, or POE	DC, AC, or 48V DC
Paystations	120V	AC

Troubleshooting Tips

No voltage reading: Check meter battery, probe contact, wire connection
Fluctuating reading: Poor connection, check all terminations
Low voltage: Voltage drop due to resistance, check wire gauge and length
Reverse polarity: Swap meter leads or check wiring

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