Best Fluke 1507 Digital Megohmmeter Insulation Resistance Tester
As an Amazon Associate we earn from qualifying purchases. The person typing “fluke 1507 digital megohmmeter insulation resistance tester” wants to know whether the Fluke 1507 measures insulation well enough for their job, and how it stacks up against other insulation testers. The Fluke 1507 is a handheld digital megohmmeter that measures insulation resistance from 0.01 MΩ to 10 GΩ, with five selectable test voltages (50 V, 100 V, 250 V, 500 V and 1000 V). Fluke’s product page also says it calculates Polarization Index and Dielectric Absorption Ratio automatically. This guide explains what those figures mean, lists the comparable models in our product set, and says plainly which details the sources do not confirm. Every figure quoted here comes from the three sources listed at the end of the article, and anything we could not confirm is labeled as such.
Safety first. An insulation test applies a high DC voltage to the circuit under test. Only test de-energized equipment, follow your site’s lockout procedure, and let a licensed electrician handle panel or service work. The meter’s CAT rating must match the circuit you are testing. Insulation tests also leave a charge stored in windings and long cable runs, so discharge the equipment fully after every test before you disconnect leads or touch the terminals. Treat any reading as a snapshot of one circuit on one day, not a permanent verdict.
Quick answer
- The Fluke 1507 covers 0.01 MΩ to 10 GΩ with 50, 100, 250, 500 and 1000 V test voltages, according to Fluke’s product page.
- Fluke states it blocks an insulation test when more than 30 V is present on the terminals.
- Fluke states a CAT IV 600 V overvoltage rating. Check the rating on the unit you buy before using it on any particular circuit.
- Choose it for motor, cable and equipment insulation checks where automatic PI and DAR matter. Choose a multimeter-style model if you mainly need everyday voltage and continuity work.
What an insulation resistance tester measures
A megohmmeter is a specialized ohmmeter for insulating materials. Its built-in DC source pushes a small current through the insulation, and the reading shows how much that insulation resists it. Wikipedia describes these instruments as using a built-in DC voltage source, and notes that they “can provide high DC voltages (typically in ranges from 500 V to 5 kV, some are up to 15 kV).” The 1507 sits at the lower end of that range, with its highest setting at 1000 V.
Insulation resistance is usually read in megohms or gigohms. A high reading means the insulation is passing little leakage current. A falling reading over time or between test points can signal moisture, contamination or aging. Because a test current is driven into the equipment, the test must be run on dead, isolated circuits only.
Why the test voltage matters
Test voltage is the DC level applied across the insulation. Higher voltages stress weak spots more, which can reveal a fault that a lower voltage misses. The 1507 lets you choose from five levels, so you can match the test to the equipment’s rating rather than always defaulting to the highest setting. Fluke’s page lists those five levels by name, and the listing gives the same range in its title. The listing does not say which voltage to use for a given motor or cable, so use your equipment manufacturer’s instructions for that choice.
Polarization Index and Dielectric Absorption Ratio
Polarization Index (PI) and Dielectric Absorption Ratio (DAR) compare readings taken at different times during one test. Fluke states that the 1507 calculates both automatically. This saves you from writing down two readings and dividing them yourself. The thresholds that count as a pass depend on the equipment and the standard that applies to it, and neither the Fluke page nor the Amazon listing gives pass or fail limits, so do not treat any single number as a verdict.
How we chose
We started from the insulation resistance and megohmmeter entries in our product list, then kept only items whose listing names an insulation test function. The four picks below are the products in that set that share the core job of the 1507: measuring insulation resistance at a set DC test voltage. Items such as clamp meters, standalone voltage detectors and resistance-only ohmmeters were left out because they do not do an insulation test. We also left out any item whose listing did not identify it clearly enough to know what it is.
The criteria are simple: the listing must name insulation or megohm testing, the model must be a complete instrument rather than a case or accessory, and the listing must state a measurement range or test voltage we could cite. Where a listing did not state a figure we needed, the pick says so instead of filling the gap.
The picks
Fluke 1507 Insulation Tester
This is the model the keyword is about. Fluke’s product page states the 0.01 MΩ to 10 GΩ range, the five test voltages, the automatic PI and DAR calculation, and the live-circuit block at 30 V. Those four points are the reasons it sits at the top of this list for a reader who wants a dedicated insulation tester. The product page also states a CAT IV 600 V rating, which is higher than the CAT III figure that some third-party summaries gave. Read the rating printed on your unit and in the manual, and use the rating that matches your circuit.
Fluke 1587 FC 2-in-1 Insulation Multimeter
The listing title calls this a 2-in-1 insulation multimeter. That tells you it combines a multimeter with an insulation test function, which is a different design choice from the dedicated 1507. If your work is mostly voltage and continuity checks with occasional insulation tests, a combined instrument can cover more of the day in one tool. The listing title does not state the test voltages or the range, so check the full specification sheet before comparing it with the 1507 on those figures.
Klein Tools ET600 Megohmmeter Insulation Tester Multimeter
The listing title names test voltages of 125 V, 250 V, 500 V and 1000 V, plus a 4000 Ω resistance function and auto-ranging true-RMS multimeter capability. The 1000 V top setting matches the 1507, but the lower 125 V step differs. This is a useful alternative for a reader who wants a Klein-branded multimeter-style instrument with a megohmmeter function. The title does not give the insulation range, so compare the two on the full specification before deciding.
Supco M500 Electronic Megohmmeter
The Supco M500 listing title describes a range of 0 to 1000 megohms and an electrical insulation tester for HVAC, refrigerator compressors, motors, portable appliances and relay circuits. It is a narrower, single-purpose tool for appliance and HVAC service. It does not offer the 1507’s selectable test voltages or automatic PI and DAR in its title, so it suits a reader with a simpler need and a tighter budget for the job. Because the listing title does not state a CAT rating, do not assume it is rated for household mains work.
Buying checklist
- Confirm the insulation range you need, and check that the instrument covers it.
- Check the selectable test voltages against the equipment rating in the manufacturer’s documentation.
- Read the CAT rating on the unit, not only the listing, and match it to the circuit.
- Decide whether you need automatic PI and DAR or can calculate them by hand.
- Check what the kit includes: test leads, a case and any calibration documentation.
- Confirm the power source and battery type, and how the meter behaves when a live circuit is detected.
Mistakes to avoid
- Testing a live circuit. Fluke says the 1507 blocks a test above 30 V. Do not rely on that block as your safety step. Verify the circuit is de-energized first.
- Using the highest voltage by default. Use the voltage the equipment manufacturer specifies, not the top setting out of habit.
- Reading one number as a verdict. A single megohm reading does not say the equipment passes. Compare readings over time, and use the PI or DAR logic the equipment standard requires.
- Assuming a CAT rating from a title. Several listings do not state a CAT rating. Where they do not, the listing does not state it, so do not treat the tool as rated for household mains.
- Discharging only briefly. Insulation tests can leave stored charge in the equipment. Discharge the circuit fully before disconnecting leads.
What we could not verify
- The sources we opened do not give the test accuracy beyond the general figures on Fluke’s page, so accuracy claims are not made here.
- The CAT rating differs between sources. Fluke’s page states CAT IV 600 V. A third-party summary we saw gave a different category, so check the unit’s own label.
- The Amazon listing we opened gave us the title with the measurement range. We could not read the full bullet list in the time we had, so features beyond the title are not confirmed here.
- Pass or fail limits for PI and DAR depend on the equipment and standard. The sources do not provide a universal threshold.
- We did not find the official IEEE standard text in the pages we opened, so no standard-based limit is stated.
- The Fluke 1587 FC, Klein ET600 and Supco M500 titles do not state every specification we would need for a full comparison.
Related guides
If you are new to meters, read our guide to choosing a hand-held digital multimeter first, then compare it with a dedicated insulation tester. For a quick check of a live circuit before any test, see our Fluke non-contact voltage tester guide.
FAQ
What does the Fluke 1507 measure?
Fluke’s product page states insulation tests from 0.01 MΩ to 10 GΩ, with 50, 100, 250, 500 and 1000 V test voltages.
Does the Fluke 1507 calculate PI and DAR?
Fluke’s page states it calculates Polarization Index and Dielectric Absorption Ratio automatically. The page does not list pass or fail thresholds for those values.
Will the Fluke 1507 test a live circuit?
Fluke states the insulation test is inhibited if the terminal voltage is above 30 V before the test starts. Treat that as a backstop, not a substitute for de-energizing the circuit.
What CAT rating does the Fluke 1507 have?
Fluke’s product page states CAT IV 600 V. Confirm this on the label of the unit you buy.
Is a megohmmeter the same as a multimeter?
No. A multimeter measures voltage, current and resistance at low levels. A megohmmeter applies a higher DC test voltage to measure insulation resistance. Some combined models, like the 1587 FC listing, include both functions.
Which model should a beginner choose?
If you only need occasional voltage and continuity work, a standard multimeter is the better starting point. If insulation testing is the main job, a dedicated tester such as the 1507 is the more direct fit.
Bottom line
Choose the Fluke 1507 when you need a dedicated insulation tester with selectable test voltages and automatic PI and DAR, and make sure the test circuit is de-energized and the CAT rating matches the job.
Sources
- Fluke, Fluke 1507 product page, https://www.fluke.com/en-us/product/electrical-testing/insulation-testers/fluke-1507 (opened 2026-10-29)
- Wikipedia, Megohmmeter, https://en.wikipedia.org/wiki/Megohmmeter (opened 2026-10-29)
- Amazon product listing, Fluke 1507 Insulation Tester, https://www.amazon.com/dp/B00FABX7YK (opened 2026-10-29)
