MM400

Klein Tools has always set the standard for professional-grade tools, and this multimeter is no exception. From the moment you pick it up, the build quality speaks volumes — rugged, solid, and clearly designed for real-world job site demands. Accuracy is spot on, whether you're measuring voltage, current, resistance, or continuity. The readings are consistent and fast, with virtually no lag, which makes troubleshooting efficient and reliable. The auto-ranging feature works flawlessly and saves time in the field. Durability is another standout. This meter is clearly built to last, with a reinforced casing that can handle drops and daily wear. The display is sharp and easy to read, even in dim lighting, and the controls are intuitively laid out for one-handed use. Packed with features like true RMS, backlit display, and a wide measurement range, it’s everything a professional or serious DIYer needs — without the unnecessary fluff. Klein Tools continues to prove they understand what technicians actually use and value. In short, this meter nails it: fast, accurate, durable, and thoughtfully engineered. If you want a meter you can count on day in and day out, this is it.

I have been using this little orange electron wrangler for a few months now and I have a few preliminary opinions formed. First off, this thing is pretty cheap, and I would not recommend it for a professional as a primary meter (obviously), or even the serious DIY'er. Mainly, it lacks range, overall accuracy, and true RMS functionality. However, for the home-gamer, or as a cheap backup to your Fluke, this little guy is pretty great. The good: The readout is clear and crisp, and the backlight works wonderfully. The lead wires are supple, and the ends do fit into household outlets once you remove the plastic CAT IV covers (duh). The included K-type thermocouple has a long (over 12-inch) reach, and it agrees to within 1 degree Fahrenheit with my other instrumentation up to about 400 degrees. The continuity test is pretty decent, and it has a light and a beeper, which is great in environments where hearing protection is required. The rubber case that surrounds most of the unit is grippy and seems fairly durable. It says the meter can be dropped up to a meter, which could get confusing, but I think I'll go with the metric interpretation in this case. The stand is pretty awesome as well; it pops out of the back and has rubber feet that effectively hold the meter in a good viewing position on most semi-level surfaces. Lastly, this meter is pretty feature-packed, having all the standard gizmos in addition to AC/DC current, frequency, duty cycle, thermocouple temperature, capacitance, and diode testing. It can do quite a bit, even if it can't do it as well as a $200 meter. Safety: This meter features two slow-blow ceramic fuses, which are the industry standard for safety, and will protect you from shrapnel should you accidentally touch the leads to a 1.21-gigawatt power source in continuity mode. Caveats: The HOLD function on this meter is a joke; you put the leads on the circuit, press the HOLD button, and the instantaneous reading is frozen in the display for you to read. Contrast this to Fluke's feature where you push the HOLD button and then hook up the leads and the meter gives you a beep and holds your number on the display once the readings stabilize. Maybe Fluke has a pending patent on this technology - it would be interesting to find out why other companies aren't doing something similar. Still, is this function worth the extra $150+ to someone who isn't a professional? Probably not. Next, the continuity/low resistance tester has a small amount of lag in it. That is, you must create a complete circuit for more than about half a second for the unit to beep, indicating low resistance. This may not be an issue for you, but if you find yourself dragging a lead across a set of pins trying to trace a short, you'll quickly find the lag in the continuity indicator to be a bit of, well, a drag. Still, some of the higher-end meters also have this issue, so it definitely isn't a damnable offense for this little guy to be lacking in this area as well. But, it is something you ought to consider before making your purchase. Overall: This is a decent little meter that can do 90 percent of the things a DIY'er will ask of it.

Bought the MM400 to replace my aging Beckman Circuitmate DM27 which I was using for general home use. I'm really happy with the Klein MM400, it's small and easy to handle, has nice quality probes and feels solid. The simple dial and auto range feature makes it easy to use and the on demand back-light and auto-shutoff to save battery are features I was looking for in a new DVM. The one inconvenience is that the unit defaults to AC for and voltage and current measurements. This makes sense as the unit is intended for electricians who most often deal with AC installations. Most my usage is for DC measurements so I have to remember to press the SEL button to change it, no biggie, I'll survive. I compared accuracy for measurements of voltage, current, capacitance and frequency between the Klein and my older Beckman and the readings were consistent with in a few tenths of a percent between the two. I couldn't verify the resistance accuracy as that's the feature that failed on my old Beckman. I wouldn't choose this basic unit for precise computer or circuitry troubleshooting but for electrician work, auto repair, or even typical home hobby electronics it would be fine.

Overall, it does what I need, seems accurate and well-designed, has a nice backlight, and I know Klein is a great brand. What I wish I'd known before I bought a Klein multimeter is that it defaults to AC in all current and voltage modes, and requires a press of the SEL button to toggle to DC. And even when switching between mA and µA, for example, it returns to AC. There's no way to change this default. As someone who works exclusively with small DC electronics, this is a noteworthy inconvenience. The number of times I've been flabbergasted by my reading, only to realize I didn't switch to DC yet again... has me wondering if I should have chosen a different brand.

Worked well for me, liked it enough to by an upgraded model for dedicated use at another location.

I was looking for a multimeter that is accurate and easy to use around the house for a person who is not a professional electrician. This product meets all of my needs, especially when used in conjunction with “how to” videos from the internet. I especially like how the controls are laid out and that the screen is bright and easy to read. I haven’t used the thermocouple yet but it seems to read the ambient air temperature accurately and is a nice add on, even though it is not a high-demand item for me. This multimeter is a terrific value that puts you way ahead of the lower-end units. I highly recommend it!

Between Klein and Fluke: Klein is better priced and they make decent tools.

This multimeter is very useful.

Needed an additional mobile DMM as a complement to my benchtop Fluke. I was positively surprised of the qualities and versatility of this very affordable tool. An unusual feature is the backlit display of surprisingly good quality. Only little detail I will upgrade is to get a set of silicone test leads. The included leads are good PVC but still PVC. If you are used to silicone leads, there's no way back.

Meter works well, very solid construction and very good dial, which has been the failure for me on many cheap meters. As well, it uses an normal AAA battery vs. useless button cells. My only complaint is that some of the display text or symbols needs to be larger for those of us with old eyes and that have difficulty reading text without glasses. It is such a PITA to see if one is in AC or DC mode as the DC symbol is so faint and small. What it means is that the unit has to be switched Off and then to Voltage and then the Select button pressed to get to DC, but sadly the DC setting will not stay at DC if turned off or to another mode. I see a new and more expensive model has a direct DC Voltage Setting, as others have also complained about this MM400's AC to DC switch. Great meter though if you can get it on sale vs. regular price.

works well, easy to use for amateur [probably over the top for me], except the heat probe would be more useful if it had a longer tip with higher temp range; had to buy another to try

Ce multimètre numérique Klein Tools MM400 est sorti en 2016. Il s’agit d’un modèle à évaluation automatique de la sensibilité, de catégorie III 600V, classe 2 et avec double isolation. Klein Tools est une marque américaine mais ce multimètre est fabriqué en Chine. N'ayant pas le budget pour un Fluke ou un Metrix, je me suis tourné vers ce modèle, vendu 55€. Ce Klein Tools MM400 mesure 15,3cm haut x 7,8cm large x 4,5cm profondeur. Il pèse 230grs. Le multimètre est livré avec : - Fils de test pour mesurer tension, intensité, résistance etc. - Thermocouple pour mesurer la température - 2 piles AAA - Notice en français Ce multimètre est fait de matériau plastique. L’appareil est néanmoins robuste, avec un commutateur de sélection de bonne qualité. La coque moulée protège le MM400 des chutes jusqu’à 1m de hauteur. Pour insérer les piles, il faut dévisser le capot arrière à l’aide d’un tournevis cruciforme. Un pied rabattable fixé sur ce capot permet de maintenir le multimètre droit pour faciliter la lecture des résultats. La housse n’est malheureusement pas fournie. Elle est vendue 20€ sous la référence Klein Tools 69401. Idem pour la sangle de transport (référence 69417). Caractéristiques techniques de l’appareil : - Mesure de la tension jusqu’à 600V - Courant jusqu’à 10A - Résistance jusqu’à 40MΩ - Températures comprises entre -18°C et +538°C Bon point : le Klein Tools MM400 est un multimètre auto-range. En d’autres termes, il s’adapte automatiquement à ce qui est mesuré, sans avoir à toucher le commutateur de sélection. L’appareil possède un écran rétroéclairé et il s’éteint automatiquement après 30 minutes d’inactivité. Ce multimètre permet une grande variété de mesures : ampérage, résistance, voltage (alternatif ou continu), capacité, température, fréquence, test de continuité (avec témoin sonore) et test de diodes. Attention, le thermocouple K fourni fonctionne pour des températures inférieures à 180°C. Pour des températures supérieures, il faut utiliser un thermocouple adapté. En cas de surcharge, « OL » s’affiche à l’écran. A l’intérieur du multimètre, 2 fusibles préviennent des chocs électriques : 500mA/600V pour la prise jack VΩ et 10A/600V pour la prise jack 10A. J’utilise le Klein Tools MM400 en remplacement d’un multimètre de poche d’entrée de gamme. Mon frigo combiné Bosch KGN étant par ailleurs tombé en panne, j’avais besoin d’un appareil précis pour repérer les composants défectueux. L’évaporateur du frigo était régulièrement pris en glace, et le multimètre m’a permis d’identifier la panne : la résistance de dégivrage et la sonde CTN d’ambiance étaient bonne, mais la sonde PTC de l’évaporateur et le fusible thermique étaient hors service (affichage « OL » sur le multimètre). Le MM400 me permet aussi d’identifier correctement le câblage électrique de mon domicile. Sur certaines prises de courant, il y a en effet une inversion entre le fil de phase et le neutre. En conclusion, le Klein Tools MM400 est un multimètre complet, robuste et qui offre un bon rapport qualité/prix. Plus accessible qu’un Fluke, il rend de nombreux services et permet de dépanner soi-même les problèmes électriques et électroniques du quotidien. Points positifs : + Robuste + Grande variété de mesures possible + Auto-range + Bon rapport qualité/prix + Extinction automatique + Notice en français + Piles AAA faciles à remplacer Points négatifs : - Assez volumineux - Étui de transport non fourni et onéreux Climaxe