Metravi ST-09 Socket Polarity Tester
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A. Product Overview
The Metravi ST-09B is a smart electrical socket tester used to identify whether an AC socket has been wired correctly. It checks the Line, Neutral and Earth arrangement and provides a clear visual indication when it detects an incorrect connection, missing conductor or socket sequence problem.
Unlike a basic polarity indicator, the ST-09B also measures phase voltage between Line and Neutral, leakage voltage between Neutral and Earth and RCD or GFCI trip performance. Its large high-definition LCD displays the measured values, socket wiring status, trip time and RCD trigger current.
The tester is suitable for routine electrical maintenance, office socket inspection, wall socket testing, power strip testing and electrical safety checks in commercial and industrial facilities.
Main Features
- Three-hole socket Line, Neutral and Earth detection
- Socket connection and socket sequence testing
- Phase voltage measurement
- Neutral-to-Earth leakage voltage measurement
- RCD and GFCI test function
- RCD trigger-current display
- Trip-time measurement
- Large backlit LCD
- Backlight colour changes when a problem is detected
- Automatic Data Hold after approximately three seconds
- Automatic shutdown after approximately five minutes without operation
- Compact and portable body
- CAT II 300V safety rating
- Battery-powered operation
B. Working Principle
The Metravi ST-09B is plugged directly into a compatible three-hole AC socket. After connection, the tester detects the electrical relationship between the Line, Neutral and Earth terminals.
Its internal circuitry analyses the socket wiring sequence and compares the detected connections with the expected correct arrangement. The result is shown on the LCD through wiring symbols, status messages and backlight colour changes.
The instrument also measures:
- Phase voltage between Line and Neutral
- Leakage or potential-difference voltage between Neutral and Earth
- RCD or GFCI trip current
- Time taken by the protective device to trip
When the RCD test button is pressed, the tester introduces a controlled test condition intended to operate the connected residual-current protective device. The display then indicates the trigger current and trip time.
The Data Hold function automatically locks the measured data approximately three seconds after the tester is plugged into the socket, making the result easier to read.
C. Why It Is Used
The Metravi ST-09B is used to identify socket wiring faults that may affect electrical safety, equipment operation or protective-device performance.
Incorrect Line, Neutral or Earth connections may lead to unsafe socket conditions, ineffective earthing, equipment malfunction or an increased risk of electric shock. A socket tester allows these problems to be detected quickly without carrying out a lengthy manual inspection for every outlet.
It is also used to verify whether an installed RCD or GFCI protection system trips during a test condition. This helps electricians and maintenance personnel assess whether the protective device responds as expected.
Common Reasons for Using the ST-09B
- To verify correct socket polarity
- To check Line, Neutral and Earth connections
- To identify missing or incorrectly connected conductors
- To test wall sockets after installation
- To inspect electrical outlets during maintenance
- To check sockets before connecting sensitive equipment
- To measure phase voltage
- To check Neutral-to-Earth leakage voltage
- To test RCD and GFCI trip operation
- To reduce the time required for socket fault diagnosis
The ST-09B is a diagnostic instrument. Any wiring fault identified by the tester should be inspected and corrected by a qualified electrician.
D. Suitable Buyers
Electricians
Electricians can use the ST-09B during new installations, repair work and periodic socket inspections.
Electrical Contractors
Electrical contractors can use it to verify multiple sockets before handing over residential, commercial or industrial projects.
Maintenance Engineers
Facility and maintenance engineers can use the tester for routine socket inspection in factories, offices, laboratories, warehouses and institutions.
Safety Officers
Electrical safety personnel can use it as a preliminary checking tool during workplace safety inspections.
Facility Management Companies
Facility service providers can use the tester while inspecting office buildings, schools, hotels, hospitals and commercial properties.
Laboratories and Educational Institutions
Laboratories, technical institutes and training centres can use it for socket testing and electrical maintenance activities.
Home Inspectors and Property Managers
Property inspectors and building managers can use it to identify basic socket wiring problems before arranging corrective electrical work.
Electrical Instrument Dealers
Electrical and industrial instrument suppliers can offer the ST-09B to customers requiring a portable socket polarity, leakage and RCD testing device.
Technical Specifications
| Parameter | Specification |
|---|---|
| Phase voltage range | 30V to 260V AC |
| Phase voltage frequency | 45Hz to 65Hz |
| Phase voltage accuracy | ±3.0 percent plus 2 digits |
| Leakage voltage range | 0V to 99V AC |
| Leakage voltage frequency | 45Hz to 65Hz |
| Leakage voltage accuracy | ±2.0 percent plus 2 digits |
| Trip-time range | 10ms to 1000ms |
| Trip-time accuracy | ±2.0 percent plus 4 digits |
| RCD test current | More than 30mA |
| Display | Large high-definition backlit LCD |
| Data Hold | Automatically locks after approximately three seconds |
| Automatic shutdown | Approximately five minutes without operation |
| Operating temperature | 0°C to 40°C |
| Operating humidity | 20 percent RH to 75 percent RH |
| Maximum operating altitude | 2000 metres |
| Safety category | CAT II 300V |
| Power supply | Two 1.5V AA alkaline batteries |
| Weight | Approximately 103 grams |
| Dimensions | 67mm x 65mm x 75mm |
These specifications are listed on page 2 of the ST-09B catalogue.
Frequently Asked Questions
1. What is the Metravi ST-09B used for?
The Metravi ST-09B is used to check electrical socket polarity, Line, Neutral and Earth connections, phase voltage, leakage voltage and RCD or GFCI trip operation.
2. What type of socket can the ST-09B test?
It is designed for compatible three-hole sockets with Line, Neutral and Earth connections.
3. Can it identify incorrect socket wiring?
Yes. It analyses the socket wiring sequence and indicates whether the connection is correct or whether a wiring problem is present.
4. Does it detect a missing Earth connection?
The tester is designed to identify Line, Neutral and Earth connection conditions, including missing or incorrectly connected conductors.
5. Can the ST-09B measure socket voltage?
Yes. It measures phase voltage between Line and Neutral from 30V to 260V AC at 45Hz to 65Hz.
6. Does it measure leakage voltage?
Yes. It measures voltage between Neutral and Earth from 0V to 99V AC.
7. What is the RCD test function?
The RCD test function applies a controlled test condition to check whether the connected residual-current protective device trips correctly.
8. Can it test a GFCI?
Yes. The catalogue specifies both RCD and GFCI testing functions.
9. Does it display RCD trip time?
Yes. It measures and displays trip time from 10ms to 1000ms.
10. Does it show the RCD trigger current?
Yes. The display can indicate the RCD trigger current during testing.
11. Will the RCD test disconnect the power supply?
The test may operate the connected RCD or GFCI and interrupt power to the protected circuit. Sensitive equipment should be disconnected or safely shut down before performing the trip test.
12. Does the tester have Data Hold?
Yes. The meter automatically locks the measured data approximately three seconds after being plugged into the socket.
13. Does the display indicate wiring problems clearly?
Yes. The LCD shows socket wiring information, and the backlight colour changes to indicate detected problems.
14. Does the ST-09B switch off automatically?
Yes. It shuts down after approximately five minutes when no operation is performed.
15. What batteries does it use?
It uses two 1.5V AA alkaline batteries.
16. Is the Metravi ST-09B portable?
Yes. It weighs approximately 103 grams and has compact dimensions of 67mm x 65mm x 75mm.
17. What is its electrical safety rating?
The tester is rated CAT II 300V and is listed as conforming to EN61010-1, EN61010-2-030 and EN61326-1.
18. Can it be used for industrial socket maintenance?
It can be used for compatible sockets within its specified voltage range and CAT II rating. The user should confirm socket type, voltage and installation category before testing.
19. Is it suitable for live electrical testing?
The tester is designed to be connected to energised sockets for measurement. It should be used only by a competent person who follows electrical safety procedures and the manufacturer’s operating instructions.
20. What is the difference between the ST-09 and ST-09B?
The basic ST-09 is primarily a socket polarity and wiring indication tester. The ST-09B 2024 model includes a digital LCD, voltage measurement, leakage-voltage measurement, RCD and GFCI testing, trip-time measurement, Data Hold and additional socket diagnostic functions.