Review of the Klein MM400 multimeter - Page 1
Forum section: electronics / testgear

author: calzap
author_rank: Frequent Contributor
timestamp: March 18, 2021, 06:06:22 pm
content: I bought the Klein MM400 to use in my tool shop and in the field. The electronics bench is in another building, and the meters there are an Agilent U1241AN and GW Instek GDM-461. At the time, the meters in the tool shop were an Extech 310 and Craftsman 82372. The Craftsman meter is designed to be hand-held, is mostly for building wiring work and has a clamp-on ammeter. The Extech is the real workhorse and has survived many drops, over-currents and other abuses. However, the Extech is not autoranging and can’t measure capacitance. And at times, a second multimeter for the shop bench is needed.Klein is a brand I trust for hand tools, and their meters are reasonably priced on Amazon. The MM series consists of 4 meters: MM300, MM400, MM600 and MM700. The latter two are significantly larger, including larger displays, than the first two. The MM300 is a basic, manual-range VOM that also measures AC amps and DC mA.The MM400 has all the additional features that I wanted: autoranging, capacitance, uA to 10 A for AC and DC, and a UL, ETL or CSA listing. It also measures some things that I probably won’t use much in the shop like temperature (comes with a thermocouple probe), frequency and duty cycle. The LCD display is big enough (12.5 mm high digits) with good contrast and wide viewing angle. The backlighting is excellent and has auto-extinguish set at 3 minutes. The meter has some other nice features like hold, max, min and range-override. It’s rated CAT III. The cost was US$45 from Amazon.The MM600 and MM700, in addition to being larger, are rated CAT IV and have higher drop and water resistance ratings. They also have more frequency and capacitance range than the MM400. Only the MM700 can make true RMS measurements. All the models are 4,000 count (3 and ¾ digits) except the MM300 is 2,000 count. Good enough for shop and field use, but far less than my Agilent at 10,000 and GW Instek at 22,000. All Klein models are ETL listed.Measurement extremes for the MM400 are VAC: 1 mv - 600 V in 4 ranges; VDC: 0.1 mv – 600 V in 5 ranges; AC/DC current 0.1 uA – 10 A in 5 ranges; ohms: 0.1 – 40 M in 6 ranges; capacitance: 10 pF – 200 uF in 5 ranges; frequency: 0.001 Hz -50 kHz in 5 ranges; duty cycle: 0.1% - 99.9% in 1 range; temperature: -18 C to 538 C in 1 range. Stated accuracy for measurements is in the range of 1-3% except for 3-5% for capacitance. The upper end of the capacitance range is low for a meter promoted for electricians. One of the most common capacitance measurements made by electricians is on motor start/run caps. Some of these can be more than 500 uF.I checked accuracy for DC voltage, current and resistance with my DMMCheck standard. For the 5.0000 V standard, the reading was 4.97 V, which was within spec. For the 0.9997 mA standard, the reading was 0.98 mA, which is a little out of spec. The resistance standards were 999.5 ohms, 10.005 kohms, and 100.05 kohms. The readings were 1001 ohms, 10.01 kohms and 100.0 kohms, respectively. This performance is well within spec and comparable to my GW Instek and Agilent meters.I don’t have a capacitance standard but do have a DER EE LCR meter. So, I checked the Klein against the DER EE on a group of capacitors ranging from 0.0001uF through 100 uF. At 0.01 uF and less, they were in good agreement. Beyond that, the Klein consistently read higher by an average of 16%. The DER EE gave readings closer to the label value of the capacitors.I checked frequency readings using a GW Instek GFG-8250A signal generator using a 5 V sine wave at 10, 100, 1000, 10000 and 50000 Hz. The Klein display matched the signal generator display at all frequencies.The meter itself feels robust in the twist and shake test. The center knob has good positive detents. One complaint is having the Off position in the middle instead of extreme clockwise or counterclockwise. If the backlight is on and the knob is moved from a measurement on the left to one or the right or vice versa, the knob passes through Off, extinguishing the light … a minor annoyance. The primary mode for V and A is AC, which makes sense for electricians, the target customers. DC mode is accessed by pressing the SEL button. If the knob is moved, the meter immediately jumps back into primary mode. The meter does have a 30-minute auto-power-off, which can be deactivated.The meter came with a pair of GP AAA batteries which are presumed to be alkaline, but it’s not stated on them. A nice pair of CAT IV probes was included. I’m unlikely to use the probes much, preferring Parrot probes for routine work and Agilent microprobes for fine work.Pictures below show the meter front with supplied probes, back with Parrot probes in the grooves, back with AAA batteries in the grooves, and backside of the PCB. The front is pretty conventional. The orange “rubber suit” is not removeable. The back has the expected flip-out stand. It’s wide enough that the meter is pretty stable when the knob is turned or the buttons are pushed.The top of the backside is interesting. The dark object in the middle is an attachment point for an optional lanyard. The two, protruding grooves on each side can serve several purposes. The primary purpose is to hold the supplied probes. The small slit across each groove accommodates a probe flange. And, yes, they will hold Parrot probes as well as Klein’s probes. Leave the probes plugged-in, wrap the cords around the plug-end of the meter, snap the probes into the grooves, and you’ve got a compact package. Another function is to give the meter a slight slant when it’s on its back, which improves readability. The grooves will also hold a spare pair of AAA batteries, but not simultaneously with the probes. I’m never far from spare batteries in the field, but for some, it could be a handy feature.The battery cover is held on by a single machine screw. The battery bay is a recess in the back cover. The back cover is held on by 6 coarsely threaded sheet metal screws. When the back is lifted away, the positive and negative contacts, which are soldered to the PCB, slip-out through a couple of holes in the bay. The holes give battery leakage access to the PCB though. Some of you may recognize the PCB and can tell us who made it … please do. I doubt that Klein has a multimeter factory. The chip near the middle is a DM1106EN multimeter chip, and chip near the top is a 24LC02B EEPROM. The overcurrent and overvoltage protection look adequate and are probably just enough to get the ETL stamp.There are two fuses, both fast blow, rated 600 V, and ceramic encased. The 10 A fuse is 6x32 mm and is widely and cheaply available. The 500 mA fuse is 5x20 mm and is another story … there’s Klein’s (actually ASTM’s) version of it. It’s widely available in the US, but costs about US$10. I found the peaktech-rce.com version for about US$2 each at their website and elsewhere in Europe. But only in a 10-pack, and shipping to the US was about US$40. I finally gave up trying to find a bargain and ordered three at US$10 each (+SHT) from zoro.com.In summary, the Klein MM400 will be just fine for the tool shop and field. It will measure what I need and with enough accuracy for the purpose. I would not want it for a primary meter on an electronics bench.Mike in California