The Klein Tools MM100 is a basic multimeter from this popular manufacturer, which finds best usage around the home. It is one of their most basic meters, built mainly for light use or occasional work, and sports a manual ranging function only. This will suit standard wiring duties around the home, office, farm, garage or building maintenance, for example.
- AC / DC voltage to 600V
- DC current to 10A
- DC low-volt accuracy: ±0.5%
- Continuity buzzer
- Diode test
- Display hold
- Battery test
- CATIII rated to 600V
- Size: 5.7” (146mm) x 2.8” (70mm) x 1.8” (45mm
- Weight: 8oz (227g)
- Probe leads
- 9V batter
- Basic instructions
In-depth Review of the Klein MM100
The most obvious thing aside from it being a very basic multimeter is the lack of auto ranging ability. This might be an issue for those new to electrics, since you’ll need to select the right range before you can test successfully. Most meters today are auto ranging, so it shows how basic a device this is.
That said, manual ranging usually works faster and, once you have the hang of it, using the Klein MM100 should be easy enough. Most people only check voltage, resistance and continuity in any case, including electricians, and it does all three well enough. It can test to 600V, both AC and DC, which is plenty for most duties.
Although there is no AC current input range – meaning you can’t measure mains current – it does have DC amps, so you can check vehicle wiring and low power DC drive systems. The continuity tester is quite responsive and also loud, which is a plus. In addition is a diode checker, but this meter is not great for testing sensitive electronic circuitry as the input impedance is fairly low at 1MΩ.
DC voltage – 5 ranges (200mV-600V), 200mV: ±(0.5%+3cts)
AC voltage – 2 ranges (200V-600V), 200V: ±(1.2%+5cts)
DC current – 4 ranges (200μA-10A), 20mA: ±(1%+3cts)
Resistance – 5 ranges (200Ω-2MΩ), 200Ω: ±(0.8%+4cts)
Diode checker – 3V
Battery test outputs – 1.5V: 15mA, 9V: 30mA
cts = + counts/digits
This multimeter should be calibrated at least annually to retain these levels of accuracy.
Klein Tools are traditionally known for their hard-wearing tools and attention to detail. This is mostly true of their multimeters, although the MM100 is at the budget end of their range. It is fairly rugged and is partially enclosed by a rubber boot, but is not as sturdy as their higher end testers.
It is not as tough as the MM1000, for example, although that model is built for electricians and is three times the price. The 100 is good enough for the home and also has lead storage built into the back, as well as long stock leads. These come with protective boots that can be removed for harder to reach areas.
Display and Labels
The display on the MM100 is clear and is a 2000-count screen, meaning it can show to 1999 (or 19.99V, for example). There is no backlight in the display. Range icons are displayed onscreen, along with ‘OL’ over limit, polarity and a low battery icon.
Those used to auto ranging meters might be a bit confused by the dial labels of this model at first as it is manual ranging and thus has all ranges marked up. It is not as clear as it could perhaps be, with minimal color-coding and range divisions.
Function and Performance
The dial itself has 20 positions. DC voltage and resistance have the most ranges, with 200m/2/20/200/600 DC volts (V) and 200/2k/20k/200k/2M for ohms (Ω). If you’re wondering how to test diodes, the function is on the 2kΩ range. Continuity and the battery test facility have their own stations respectively.
There was just the one button on the Klein MM100 review, the data HOLD. There are three input jack sockets at the bottom. Many meters today have four, though the milliamps and micro-amps circuits share the same input on this device.
10A (amps – red)
COM (common – black)
V/Ω/mA/µA (main jack – red)
The black lead always goes in the common input and the red lead in one of the red ones, depending what range you are testing. Just remember that everything barring 10A has the red lead in the main (right) socket.
The MM100 performs okay as it is manual ranging, and accuracy is pretty good considering the price. There is no auto shut-off mode, however, so the battery will run down faster if you forget to turn it off.
Protection is provided by two quick blow fuses, one on each of the red inputs. These are accessed through the back of the multimeter – a 250mA fuse for the mA/µA input and a 10A fuse for the 10 amp input. Meter fuses typically only blow when you try to measure amps with the wrong lead plugged into the wrong jack, or when trying to test current draw on a car.
Category rating is to level III, 600V. Mechanically, the Klein Tools MM100 is partly housed in an orange rubber boot, which helps prevent damage from drops and bangs. This tester is quite sturdy, but is naturally not as rock-solid as those of higher value.
Who is it Best Suited To?
Although it is rated to 600V, this multimeter works better on lower voltages in the home or garage. Electricians on domestic installation work could use this as a backup, but it is not suited to industry. Its battery test feature and 10A DC current range makes it fairly useful for those in the automotive trades, and it is also okay in basic electronics.
Klein MM100 Pros and Cons
- AC / DC voltage ranges separate
- Battery test feature
- Nice display
- Good brand name
- Okay for general electrics
- Manual ranging only
- No AC current
- Labels could be better
- Resistance range low
- Input sockets not great – works better with higher quality leads
- No auto-off function
Klein Tools is a quality multimeter manufacturer, yet the Klein MM100 review detailed one of their budget models. It tests volts, DC amps, resistance and continuity well and also boasts a battery and diode tester. There is nothing fancy here, however, with limited features and no backlit display.
Newcomers might be better off with the similarly priced Mastech MS8268 as it is auto-ranging and has a lead input indicator so you won’t get mixed up. A more expensive alternative with the same make is the MM200, which is also an auto-ranger and is more reliable, albeit at double price.
Optional extras for the MM100 include a handy Tradesman Pro carry case and fuse replacement kit.