does this actually place a load on the circuit for for voltage drop?

It simulates a 12,15, and 20 amp load and displays the percentage drop, according to the operating instructions.

Will this indicate open neutral or open ground when circuit is not energized?

Way late on answer this. If you’re talking about (Klein Tools RT210 Outlet Tester) then no, it has to have power on the circuit as this is not battery powered to show the tester how it’s wired.

Does this simulate and test both serial and parallel arc fault conditions?

This tester plugs into an outlet on the circuit under test, so it seems to me that automatically makes it a parallel device. Therefore it can only simulate an arc fault such as might occur in a parallel device, i.e. what you normally plug into an outlet. (A typical faulty item being be a lamp with a frayed power cord.) I believe the tester would have to be wired into the circuit in series to simulate a serial arc fault. I don't know the nature of the tester's design but it may be that tripping an AFCI unit (an AFCI outlet, for instance) with a parallel fault simulation may also prove the AFCI's ability to respond to a serial arc fault, at least in part. Disclaimer: I'm not an electrician or EE so you may want to dig farther on this subject, but I believe I have the basics right.

Does this protect trip a gfci protected receptacle with an open ground?

No it will not. No tester will trip a GFCI with open ground. You have to use the button on the receptacle/breaker in that case. Make sure the outlet is labeled with "no equipment ground."

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⚡ Power Up Your Precision: The Ultimate Circuit Analyzer for the Modern Pro

ADVANCED AFCI GFCI TESTING - Verify device safety with real-time trip time and current measurements for ultimate peace of mind.
ACCURATE VOLTAGE DROP ANALYSIS - Load test at multiple amperages to ensure your circuits deliver consistent power where it counts.
COMPREHENSIVE WIRING FAULT DETECTION - Identify open neutrals and other common wiring issues before they become costly problems.
INSTANT CLARITY WITH LARGE COLOR LCD - See wiring faults and test results at a glance—no guesswork, just precision.
BUILT FOR PROS TRUSTED FOR GENERATIONS - Crafted by Klein Tools, a family-owned brand since 1857, engineered for durability and reliability on every job.

The Klein Tools RT390 Circuit Analyzer is a professional-grade electrical tester featuring a large color LCD for easy-to-read results. It detects common wiring faults, inspects AFCI and GFCI devices with trip time and current display, and measures voltage drop under 12A, 15A, and 20A loads. Designed for North American 120V AC outlets, this battery-powered tool combines precision, durability, and trusted craftsmanship from a family-owned company with over 160 years of expertise.

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Manufacturer	Klein Tools
Part Number	RT390
Product Dimensions	25.4 x 25.4 x 25.4 cm; 222.26 g
Item model number	RT390
Size	One Size
Colour	Orange
Style	Receptacle Tester w/Voltage Drop
Finish	Brushed
Material	Blend
Pattern	Circuit Analyzer
Shape	Rectangular
Power Source	Battery Powered
Item Package Quantity	1
Certification	Cat Iii 135v, Afci, Gfci, Ul, Fcc
Included Components	3 x AAA Batteries, Instructions, and Pouch
Batteries included?	Yes
Batteries Required?	Yes
Battery Cell Type	Alkaline
Item Weight	222 g

Klein Tools RT390 Circuit Analyzer with Large LCD, Identifies Wiring Faults, GFCI and AFCI Tester, Voltage Drop, Displays Trip Time, Orange

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