What sort of test equipment should I have?
Find out what equipment you need as an electrical worker.
The range of electrical work you do, and need to test will determine the type and specifications of test equipment required.
All prescribed electrical work on installations and appliances needs to be tested in accordance with the Electricity (Safety) Regulations (ESR) 63 and ESR 90, and you must have suitable test equipment to carry out those tests.
Consider what tests you need to do.
Do some research first: ask other electrical practitioners and check out various suppliers of testing equipment.
Is the meter fit for purpose? Is it accurate? Does it have the overvoltage category rating (cat rating), resolution, test values and ranges you require?
Check out the specifications carefully and if you don’t know what they mean ask someone that does - see guide to specification terms below.
Buy reputable, robust good quality brands with after sales warranties.
Consider, size, convenience, backup and test requirements:
- a multifunction tester can conduct all the tests you may require, but the convenience of having some separate additional test instruments could also be considered
- a multifunction tester with some separate instruments could give you back up should one fail or meters could be used on separate jobs
- a compact “clip on” amp meter can be a good option. Consider the range and resolution required for current, resistance, and voltage.
Electrical test instruments
|Testing instrument measuring||Type of instrument||Comments|
|Voltage AC and DC||Dedicated voltage tester||Should be capable of reading all working voltages, both AC & DC|
|Insulation resistance||500V DC Insulation resistance (IR) tester or incorporated in multifunction tester||For testing a 400V 3 phase or 230V single phase installation a 500V DC test voltage is required as a minimum|
|Resistance||Multi-meter or incorporated in multifunction tester||Multi-meter should be rated Cat III|
|Current||Clamp-on Ammeter||Cat III clamp-on ammeter capable of reading all load requirements|
|Leakage current||Leakage current clamp-on Ammeter||Cat III high resolution clamp-on ammeter capable of reading milliamps|
|Fault loop-impedance||Incorporated in multifunction tester||Cat III or IV|
|RCD testing||Incorporated in multifunction tester||Capable of 30mA and 10mA RCD tests|
|Phase rotation||Phase rotation meter||Contactless meter offers more safety|
Multi-function test instruments
Example of test options on a multifunction test instrument.
Multi-function test instruments are now commonly available from most leading manufacturers of electrical test equipment. An internet search on multi-function electrical test instruments will provide information on available brands and models. Electrical wholesalers will also be able to help.
A single multi-function tester will provide one single instrument that can undertake all the necessary tests required by AS/NZ Standards and regulations.
Make sure you spend some time to become familiar and confident with the tester, before you use it in the field.
Specification of meter
A specification of a meter is a clearly written description of an instrument’s performance. It should quantify an instrument’s capabilities objectively under well-defined operating conditions. Look at the specifications closely and consider them all including these important terms.
|Accuracy||An instrument’s degree of accuracy — how close its measurement comes to the actual or reference value of the signal being measured.|
|Resolution||The smallest increment an instrument can detect and display—hundredths, thousandths, millionths.|
|Range||The upper and lower limits an instrument can measure a value or signal such as amps, volts and ohms.|
|Precision||An instrument’s degree of repeatability—how reliably it can reproduce the same measurement over and over.|
|Category rating of test instruments - Cat II Cat III Cat IV||Overvoltage installation categories are used to rate test instruments on their ability to resist a voltage spike. The higher the installation category the more risk that a transient over voltage spike could cause electrical and physical damage. The higher the category rating of a meter, the more protection and safety it provides the user from those risks.
Best practice when carrying out testing on low voltage installations, is to use instruments with a minimum rating of category III.
Category IV test instruments should be used when carrying out testing on power networks or “works”.
Always inspect test probes before using them
Unplug test probes from the multi-meter input jacks; verify they are shrouded and show no physical damage.
When inserted into the jacks, the connection should feel firm and secure.
Run test probes between your fingers as you visually inspect them; feel for any signs of damaged insulation.
Use test leads with minimal exposed metal at the tip to protect against electrical shorting.
Damaged test probes should not be repaired; they must be replaced. Never use damaged test probes.
Checking meter accuracy and calibration
To ensure your meter maintains operational and safe you will need to check its accuracy from time to time. Some specialist meters such as those used in low ohms testing in cardiac protected areas are required to have regular calibration through an accredited laboratory.
For common (non-specialist) meters used in installation work routine regular accuracy checks of calibration is not difficult or time consuming. It’s recommended these are carried out regularly and results noted. However, should the meter be found to be out of calibration, then it should be sent to an accredited laboratory for correction. These regular checks aren’t an alternative to accredited calibration.
- Battery checks: Use the built-in battery on-load to test battery condition. If it does not have one then check and replace your batteries as required. Keep a spare set of batteries available.
- Instrument checks: Sometimes instrument accuracy can be checked against a range of resistors of known values in addition to making comparison tests with known circuits and other meters.
For insulation resistance (IR) meters, a simple 1 Megohm resistor plus voltmeter can be used to measure the output voltage is within the required limits. Use other resistors to check readings at lower and higher ranges.
As in AS/NZS 3000:2007 188.8.131.52, the IR tester should maintain terminal voltage within +20% and -10% of nominal open circuit voltage when measuring a resistance of 1 Megohm on the 500V range or 10 Megohms on the 1000 volt range.
You could also use good quality resistors to check accuracy of the resistance readings on your multi-meter.
Comparison between different meters on the same circuit will give you an indication whether the meter readings are consistent.
For earth fault loop impedance (EFLI) and residual current device (RCD) testing some minor variation in results can be expected due to timing of test, the load and voltage fluctuations.