Download Series Circuit Measurements Be Accurate, Be Safe

Series Circuit Measurements
Be Accurate, Be Safe
By David Rainey
Navaid Lighting Associates, Inc.
Types of Test Equipment Required
Accuracy of Test Equipment
How to Determine if Your Equipment is
Accurate
Safety and Proper Procedures for Making
Measurements
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.
• 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
Class Style Step
1
1
2
1
2
2
Nominal output
amperes (A)
root mean square
(RMS)
Allowable range
(A RMS)
3
6.6
6.5 - 6.70
2
5.5
5.4 - 5.6
1
4.8
4.7- 4.9
5
6.6
6.50 - 6.70
4
5.2
5.1 - 5.3
3
4.1
4.0- 4.2
2
3.4
3.30 – 3.50
1
2.8
2.7 – 2.9
5
20.0
19.7 - 20.30
4
15.8
15.5 - 16.1
3
12.4
12.1 - 12.7
2
10.3
10.0 - 10.6
1
8.5
8.2 - 8.8
Accurate (true RMS) Equipment that doesn’t quite agree
Could One of These be the Culprit?
Swapping Clamp-on Devices Moves the Inaccurate Reading
Accuracy +or- 2%
Accuracy +or- 3% +/-0.4A
6.37 Amps
6.63 Amps Low Accuracy
Clamp-on Device
Comparison of Current Readings on
Circuit Between Two Instruments
6.60 Amps
6.63 Amps
High Accuracy Device
As Shown Previously, Accuracy of Measurement
Depends on Accuracy of Clamp-On Accessory Used
Verifying Accuracy by Direct Measurement Method
Series Circuit
!!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.
COPYRIGHT© 2004 NAVAID LIGHTING ASSOCATES
Demonstration of the Behavior of Voltage in
Airport Lighting Series Circuits
10 FAA L-850C Runway Edgelight
Fixtures and 200 Watt transformers
Series Circuit
105 + 105 = 210 watts
210 x 10% = 21 watts
210 + 21 = 231 watts
231 x 10 = 2310 watts
P/I = E
2310 watts / 6.6 amps = 350 volts
COPYRIGHT© 2004 NAVAID LIGHTING ASSOCATES
Measuring Voltage at Output of Regulator
Jumpers with Portion of Insulation Removed
for In-Circuit Voltage Measurements
Measuring Voltage to Ground
Measuring Voltage Drop Across Each Transformer
Voltage Proximity Detectors
Series Circuit
These are popular, but do not use to detect an
energized series circuit!
COPYRIGHT© 2004 NAVAID LIGHTING ASSOCATES
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