Greenlee Cm 660

Greenlee Cm 660

ByKen

Greenlee CM-660 Clamp Meter: Specs and What to Check First

As an Amazon Associate, bestmultimeter2020.com may earn from qualifying purchases. This article is informational and contains no product picks. The greenlee cm 660 is a 600 A AC true RMS clamp meter from Greenlee, and two retailer product pages we opened agree on its core ratings. It reads AC current on a 60 A and a 600 A range, measures voltage up to 600 V AC or DC, and covers resistance from 600 ohm to 60 kohm. This guide lists those numbers, shows where each figure came from, and explains what we could not confirm from the pages available to us. Read the gaps section before you buy or rely on a rating.

Quick answer

The Greenlee CM-660 is rated for 60 A and 600 A AC current, 600 V AC or DC, and 600 ohm to 60 kohm resistance, according to two retailer pages we opened. Its safety ratings are CAT III 600 V and CAT IV 300 V.

How we chose the sources

We searched for the CM-660 by model number and opened each product page that returned readable specifications. We used only pages we could open, and we left out any page that was blocked or returned no spec table.

What the CM-660 is built to do

A clamp meter measures current without breaking the circuit. You open the jaw, close it around one conductor, and read the current on the display. The CM-660 is a clamp meter first, and it also has voltage and resistance functions on the same body. That makes it a common choice for electricians who want one meter for current checks and basic circuit checks on the same job.

The AC current side is the headline feature. The Greenlee listing we opened on ITM gives AC current ranges of 60 A and 600 A. The Tallman Equipment listing gives the same two ranges. Both pages describe the jaw as 1.18 in (30 mm), which is the size the clamp can enclose. A jaw that size fits standard branch-circuit conductors and most cable bundles, but it will not enclose a large busbar. Check the conductor before you open the jaw.

Current, voltage and resistance ratings

Both opened listings give the following figures, and they match each other on every line we compared:

  • AC current: 60 A and 600 A ranges.
  • Voltage: 600 V AC and DC.
  • Resistance: 600 ohm, 6 kohm and 60 kohm ranges.
  • Frequency: voltage and AmpTip current are rated for 50/60 Hz. High-current measurement is rated for 50 to 400 Hz, as stated on the Tallman page.
  • Jaw: 1.18 in (30 mm).

The voltage rating is the number to remember for safety. A 600 V rating means the meter’s input is designed for measurements up to that level within its category. It does not mean every 600 V circuit is safe to probe with the same leads, so follow the leads and the category rules printed on the meter.

Safety category: read it before the job

Both pages list the same two safety categories: CAT III 600 V and CAT IV 300 V. In practice this means the meter is rated for measurements at the distribution level and at the service entrance, but the lower of the two ratings applies to the matching setup. CAT IV is the category for work at the origin of the installation, such as a service drop or a meter base. CAT III covers distribution panels and fixed installation circuits.

Categories are not interchangeable with voltage alone. A CAT III 600 V rating and a CAT IV 300 V rating describe different measurement locations. Before you measure at the service entrance, confirm the meter is rated for that location, and use leads and fuses rated for the same category. If the category is not clear to you, pick a meter with a higher rating or get a qualified electrician to take the reading.

Warranty and what the listing says

The ITM listing we opened gives a lifetime limited manufacturer warranty. We did not read the warranty document itself, so treat the wording as the retailer’s summary. Warranty terms can change between sellers, and the owner’s manual or Greenlee’s own warranty page is the authority.

How to take a basic AC current reading

The safe sequence for a current reading is the same on most clamp meters, but apply it with the CM-660’s manual in hand:

  1. Set the function switch to AC current and pick the 60 A range if you expect a load below that level. Use 600 A for larger loads.
  2. Confirm the leads are seated correctly and the meter is in good condition. Do not use a meter with cracked insulation or a damaged jaw.
  3. Open the jaw and enclose one conductor only. Enclosing both the hot and neutral conductors cancels the field and reads near zero.
  4. Close the jaw fully and let the reading settle. Note the range you used.
  5. Remove the meter from the conductor before you change ranges or functions.

Enclosing a single conductor is the most common mistake. A two-wire cable with both hot and neutral inside the jaw gives a small reading even when the load is large. If you see an unexpectedly low value on a loaded circuit, check the jaw position before you assume the circuit is idle.

Voltage and resistance checks

The same meter reads voltage and resistance. For a voltage check, select the voltage function, connect the leads to the points under test, and read the display. For a resistance check, power down the circuit first, isolate the component, and select the resistance function. Resistance readings on a live circuit are not valid, and a meter in resistance mode with power applied can be damaged. Always confirm the circuit is de-energized before you measure resistance.

The resistance ranges are 600 ohm, 6 kohm and 60 kohm. These cover continuity and low-resistance checks as well as some moderate-resistance tests. They do not cover the high-resistance insulation work that needs a megohmmeter, so use the right instrument for insulation tests.

Internal links for the wider workflow

If your job is a basic electrical tester check rather than a clamp reading, our guide to electrical testers covers the simpler tools that fit that task. For insulation and high-resistance checks, see our megger tester guide, which covers the meters that read those values.

What we could not verify

We opened two readable pages for this article: the ITM product page and the Tallman Equipment product page. We did not open a third, independent source. The Greenlee manual and Greenlee’s own product page were not readable through our tools, so the third source that was not available is Greenlee’s official specification sheet or owner’s manual.

Two points remain unresolved. First, a Steiner Electric listing that appeared in our search results includes capacitance as a measurement function, and the two pages we opened do not. We have not included capacitance in this article. Second, we did not confirm the accuracy figures for each range, the input impedance, or the fuse type. Look those up in the manual before you rely on them.

We also did not test the meter. This article reports what the two listings say and does not reflect our own measurements.

FAQ

What AC current ranges does the Greenlee CM-660 have?

Both opened listings give AC current ranges of 60 A and 600 A. The jaw is 1.18 in (30 mm).

What is the voltage rating of the CM-660?

The listings give 600 V AC and DC. Check the safety category as well, because CAT III 600 V and CAT IV 300 V apply to different measurement locations.

Does the CM-660 measure resistance?

Yes. The listed resistance ranges are 600 ohm, 6 kohm and 60 kohm. Always de-energize the circuit before a resistance measurement.

Is the CM-660 suitable for insulation testing?

Not as a substitute for a dedicated insulation tester. Its resistance ranges top out at 60 kohm, which is well below the range used for insulation checks. Use a megohmmeter for those tests.

What warranty does the CM-660 carry?

The ITM listing we opened gives a lifetime limited manufacturer warranty. Confirm the terms with the seller or Greenlee before purchase.

Sources

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