Klein Tools ET140
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Klein Tools RT390
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Klein Tools RT390
- Voltage:
- 135V AC
- Wiring tests:
- Open ground, open neutral, open hot, reversed hot/ground, reversed hot/neutral, and dual-open neutral-and-ground fault
- GFCI test:
- also tests 30mA ground-fault devices (26.0 to 38.0mA)
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Find on AmazonPackage details
Model: RT390
- Condition:
- Confirm new or reconditioned on the listing
- Quantity:
- Confirm package quantity on the listing
- Included essentials:
- Circuit analyzer, 3 x AAA batteries, instructions, pouch
Important limit: North American 120V 3-wire outlets only; indoor use only
Confirm condition, quantity and included accessories on the retailer’s listing.
Specifications checked November 5, 2026. Full product details
Size and package
Size and placement
- Size
- 7.1 x 2.7 x 1.5 in (17.93 x 6.93 x 3.86 cm)
- Weight
- 10.92 oz (309-311 g) including batteries
In the box
Circuit analyzer, 3 x AAA batteries, instructions, pouch
Klein Tools RT390 Circuit Analyzer
A plug-in circuit analyzer that tests outlet wiring, displays AC line voltage, measures GFCI and AFCI trip times, and runs voltage-drop tests at 12A, 15A and 20A loads.
Why people pick it
- Combines wiring-fault detection, line-voltage display, GFCI/AFCI trip testing and voltage-drop load tests in one plug-in tool
- GFCI trip time accurate to 1% ±10ms and AFCI to 1% ±20ms, per the manual
- Detects the dual-open neutral-and-ground fault that basic three-light testers miss
- Color LCD shows results plainly; 2 m drop rating, IP40 and CAT III 135V
Know before you buy
- North American 120V 3-wire outlets only; indoor use only
- Voltage-drop load tests top out at 20A, so they do not exercise 30A circuits
- Runs on 3 x AAA batteries rather than powering entirely from the outlet
Full specifications
| Voltage | 135V AC; AC voltage range 30.0 to 150.0V, accuracy 2% ±2 digits (manual) |
|---|---|
| Wiring tests | Open ground, open neutral, open hot, reversed hot/ground, reversed hot/neutral, and dual-open neutral-and-ground fault |
| GFCI test | Trip current 6.0 to 9.0mA (1% ±0.2mA); trip time 0.0 to 6.0s (1% ±10ms); also tests 30mA ground-fault devices (26.0 to 38.0mA) |
| AFCI test | Trip current 106A to 141A; trip time 0 to 400ms (1% ±20ms) |
| Voltage drop test | Load tests at 12A, 15A and 20A; load test voltage drop 0.1 to 99.9%, 3% ±2 digits |
| Display | Large color LCD |
| Designed for | North American 120V AC 3-wire electrical outlets, indoor use |
| Cord | 14AWG, 15A, 12 in (30.5 cm) NEMA 5-15P to IEC 320 C13 |
| Batteries | 3 x 1.5V AAA alkaline (included) |
| Drop protection | 6.5 ft (2 m) |
| Ingress protection | IP40 dust resistant |
| Safety rating | CAT III 135V; conforms to UL 1436, certified to CSA C22.2 No. 160 |
| Size | 7.1 x 2.7 x 1.5 in (17.93 x 6.93 x 3.86 cm) |
| Weight | 10.92 oz (309-311 g) including batteries |
| Included | Circuit analyzer, 3 x AAA batteries, instructions, pouch |
From manufacturer documentation, checked November 5, 2026. Spotted an error? Tell us.
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- Max voltage
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- Safety rating
- CAT II 120V
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Specifications & conditions
- Safety rating
- Conforms to UL 1436; certified to CSA C22.2 No. 160 (CAT rating is not marked on this tester)
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