Klein RT390 vs IDEAL SureTest 61-164

For a professional buying a circuit analyzer for loaded-voltage checks plus AFCI and GFCI functions, choose the Klein RT390. The IDEAL SureTest 61-164 adds separate conductor-impedance readings, but IDEAL’s current US page marks it discontinued, so we would not make it a new-purchase recommendation. If you only need wiring indication, line voltage and GFCI trip time, keep the RT250 and use our basic outlet-tester guide.

Quick picks: buy the missing capability

• Buy RT390 for loaded-voltage and protection-device checks. Its documented load settings are 12A, 15A and 20A, with AFCI, GFCI and a separate 30mA ground-fault function.
• Keep an existing SureTest for impedance diagnosis. The 61-164 documents hot, neutral and ground impedance; its discontinued status changes the buying recommendation, not the functions described in its manual.
• Keep RT250 for basic outlet checks. It shows GFCI trip time already; Klein’s specifications explicitly list no AFCI function. Our RT210 vs RT250 guide handles that simpler upgrade.

• Yes: RT390: loaded-voltage, AFCI and GFCI functions
• Partly: SureTest: useful impedance functions; discontinued model
• No: RT250: no AFCI function

RT390 vs SureTest 61-164: the comparison that matters

Both analyzers target 120V circuits; neither is a general-purpose higher-voltage tester.

Sources: RT390 instructions and SureTest instructions. Their display ranges and ratings do not expand their intended circuit use.

Best new-purchase choice: Klein RT390

The RT390 is our choice when the missing capability is seeing loaded voltage and percentage drop alongside protection-device checks. Its load screen presents the results for all the documented load settings, and the background turns red above 5% drop. Klein also documents detection of a dual open neutral/open ground fault.

The main limitation is diagnostic detail: Klein does not document separate hot, neutral or ground impedance readouts. The manual mentions a background load test to investigate high line impedance after an AFCI non-trip; that is not a promise of the SureTest’s conductor-by-conductor display. Buy the RT390 for its listed functions rather than assume that the word “analyzer” includes every impedance measurement.

Klein’s package list includes the analyzer, three AAA batteries, instructions and a pouch. The manual specifies a supplied 12-inch, 14AWG, 15A NEMA 5-15P to IEC 320 C13 cord and requires that supplied NEMA-rated cord. Check the cord as well as the instrument when matching the order.

Check the RT390 package at Klein Tools

IDEAL SureTest 61-164: more impedance detail, a legacy purchase

The SureTest’s useful distinction is its separate hot, neutral and ground impedance display, plus ground-to-neutral voltage, peak voltage and frequency. That makes it the more informative documented instrument for an electrician investigating which conductor contributes to a poor result. Ground-impedance testing can trip a GFCI-protected circuit, so “testing without disturbing loads” in the marketing does not apply to every function.

For a new order, the decisive issue is the manufacturer’s discontinued notice. A downloadable manual does not establish current stock or continuing service availability; confirm those directly with IDEAL if considering a legacy unit. If you need individual impedance readings, the RT390’s documented functions do not make it a like-for-like substitute.

61-164 vs 61-165: the shared manual reserves both AFCI testing and the shared-neutral test for the 61-165, and explicitly says that model is no longer available. The pictured AFCI controls in that shared document are not evidence that the 61-164 has them.

Read IDEAL’s model status and linked resources

Voltage drop: what the load settings tell you

Both instruments document the same load steps, so the largest load number does not separate them. IDEAL explains its method as measuring line voltage, applying a load, measuring loaded voltage and calculating the drop; it describes the load as short duration. Treat that as a diagnostic snapshot, not proof of sustained appliance operation or breaker capacity.

Before interpreting a result, an electrician still needs the circuit’s conductor size, run length, connected loads and the location of the receptacle relative to the panel. IDEAL lists excessive load, conductor sizing/run length and poor connections among the possible causes of high drop or impedance. A red result does not identify which of those causes applies.

Allow for the documented test conditions: RT390’s protection/load specification group gives 110V to 125V AC, 50/60Hz. Its manual can require cooling before another load test; IDEAL requires 20 seconds between insertions to maintain stated accuracy during repeated use. Those are operating constraints, not stopwatch results from thisMETER.

GFCI timing and AFCI indication have different limits

Both manuals describe a 6–9mA GFCI fault stimulus. IDEAL specifically describes a fixed resistor and displays actual test current and trip time; after power is restored, its result shows the trip time. Read that as timing at the applied stimulus, not an adjustable ramp test that finds the exact current at which a device first trips.

The separate 30mA modes concern the matching protection device; Klein warns that this protection is not inherent in every GFCI breaker. For AFCI, RT390 simulates a parallel arc, and Klein warns that a simulated signal can falsely suggest a malfunction. Some AFCIs may not trip when the run exceeds 100 ft; the manual also requires 20 seconds between AFCI events. Follow the protective-device maker’s instructions when interpreting a non-trip.

Conflicting specifications: match the instrument and its manual

IDEAL’s linked brochure and model instructions disagree on several ranges; we do not combine their largest numbers into a better specification.

There are further conflicts: the instructions’ Estimated Load on Line table reaches 20.0A, while its explanatory text says the maximum reported is 15A and gives no stated accuracy. The linked 2009 series technical manual gives CAT III @ 150V AC RMS, while the model instructions give CAT III 300V. Confirm the instrument marking and applicable revision with IDEAL before relying on a limit or using the estimated-load function for a decision.

For Klein, distinguish display range from intended use: the product page lists 135V AC, while the RT390 manual’s AC-voltage table extends to 150.0V AC. The rating remains CAT III 135V, and the manual prohibits higher-voltage supplies than its intended North American 120V outlets.

Buying guide: make the package complete

For RT390, match the supplied cord, analyzer, batteries and pouch described above. For an existing SureTest, the documented base package is the analyzer with a 1-ft extension cord, carrying case and instructions; IDEAL’s brochure identifies the cord as 61-182 and case as 61-179. Ground-continuity 61-175, isolated-ground 61-176 and alligator-clip 61-183 adapters are listed as optional; isolated-ground verification specifically requires its adapter. Confirm legacy accessory support before buying a unit for an adapter-dependent task.

1. 1

   Name the missing result

   RT390 covers loaded-voltage checks; SureTest documents individual conductor impedance.

2. 2

   Match the exact model

   SureTest AFCI and shared-neutral functions belong to the legacy 61-165.

3. 3

   Match the package

   Verify the supplied cord and the documented accessories before ordering.

Neither is an installation certificate: RT390 excludes ground quality and neutral/ground reversal, and SureTest excludes combinations of faults and reversed grounded/grounding conductors. SureTest’s false-ground indication can also appear on a correctly wired circuit within 15–20 feet of the main panel. That caveat is a reason for qualified interpretation, not a reason to dismiss every false-ground warning.

How we choose

We compared manufacturer product pages, exact-model instructions, accessory lists and the linked legacy documents. Recommendations follow documented capability and model status; physical performance has not been independently verified. Conflicting limits remain visible, and the SureTest is comparison context rather than a current pick. Read our selection method and measurement policy.

Verdict

Buy RT390 when you need the documented loaded-voltage, AFCI and GFCI functions. Keep RT250 when wiring, voltage and GFCI timing answer the question. Keep SureTest in the comparison for its impedance capability, but its discontinued status and conflicting documentation make it a legacy decision requiring confirmation with IDEAL.