1. Series Circuit Measurements Be Accurate, Be Safe
By David Rainey
Navaid Lighting Associates, Inc.

2. Types of Test Equipment Required
Accuracy of Test Equipment
How to Determine if Your Equipment is Accurate
Safety and Proper Procedures for Making Measurements

3. Test Equipment Requirements
Maintaining series circuits requires more diversity and accuracy of test equipment.
Series circuits operate at potentially high voltages and are prone to develop shorts and opens. Troubleshooting these problems requires an advanced knowledge of ohmmeters, insulation resistance testers and Amp Probes.

4. Make accurate measurements at low current 2.8 – 6.6 amps
Be able to accurately measure non-sinusoidal waveforms
Make accurate measurements of insulation resistance
Provide the ability to accurately measure photometric output of lights especially for CAT II and CAT III operations

6. Class
Style
Step
Nominal output
amperes (A)
root mean square (RMS)
Allowable range
(A RMS) 1 3
6.6 2
5.5
4.8 5 4
5.2
4.1
3.4
3.30 – 3.50
2.8
2.7 – 2.9
20.0
15.8
12.4
10.3
8.5

8. Accurate (true RMS) Equipment that doesn’t quite agree

9. Could One of These be the Culprit?

10. Swapping Clamp-on Devices Moves the Inaccurate Reading

11. Accuracy +or- 2%
Accuracy +or- 3% +/-0.4A

12. Comparison of Current Readings on Circuit Between Two Instruments
6.37 Amps
6.63 Amps
Low Accuracy Clamp-on Device
Comparison of Current Readings on Circuit Between Two Instruments

13. 6.60 Amps
6.63 Amps
High Accuracy Device
As Shown Previously, Accuracy of Measurement Depends on Accuracy of Clamp-On Accessory Used

14. Verifying Accuracy by Direct Measurement Method

15. !!CAUTION!!
SERIES CIRCUIT CONSTANT CURRENT REGULATORS ARE CAPABLE OF DEVELOPING EXTEMELY HIGH AND LETHAL VOLTAGES. THE FOLLOWING INFORMATION IS PRESENTED FOR EDUCATIONAL PURPOSES ONLY. MEASUREMENTS OF VOLTAGES IN SERIES CIRCUITS SHOULD NOT BE ATTEMPTED. NEVER UNDER ANY CIRCUMSTANCES ATTEMPT TO MAKE DIRECT VOLTAGE MEASUREMNTS OF AIRPORT LIGHTING SERIES CIRCUITS.

16. 10 FAA L-850C Runway Edgelight Fixtures and 200 Watt transformers
Demonstration of the Behavior of Voltage in Airport Lighting Series Circuits
10 FAA L-850C Runway Edgelight Fixtures and 200 Watt transformers

17. = 210 watts
210 x 10% = 21 watts
= 231 watts
231 x 10 = 2310 watts
P/I = E
2310 watts / 6.6 amps = 350 volts

18. Measuring Voltage at Output of Regulator

19. Jumpers with Portion of Insulation Removed for In-Circuit Voltage Measurements

20. Measuring Voltage to Ground

21. Measuring Voltage Drop Across Each Transformer

23. Voltage Proximity Detectors
These are popular, but do not use to detect an energized series circuit!

24. Questions?
Comments?