4 Digital Green LED Tachometer RPM Speed Meter + Hall Proximity Switch Magnet Sensor NPN for Lathe Conveyor Belt

This is a solid budget tachometer which comes with everything you need to properly measure RPM. I would say the only downsides are if you can't use the included L bracket to mount the sensor, and you must affix a magnet. For my use case, this was going onto a milling machine I was converting to run on a VFD with a modern controls system. I wanted to have an accurate tachometer, so I knew what the spindle speed was. This has worked well. Here's a tip when installing this. Power it up and before you install the magnet, move it over the sensor. If you don't get a reading, flip the magnet and retest. Mark the side which needs to be affixed to whatever you're trying to measure the RPM of, so that you ensure you keep the magnet orientated properly. I didn't do this and unfortunately it didn't work, so I had to break the adhesive loose, and redo it. I wish the magnet was marked out of the box so you knew this up front. I'm not going to knock it down, but I do wish this had a wider voltage range of say 8-26V. I am running a 24VDC control system and had to use a small 24 -> 12 volt step down converter to power only this tachometer. That was my oversight and there are other similar devices available with a wider voltage range. Other than it hanging onto the RPM for a bit after the spindle stops, I've found it to be quite reliable and accurate. The camera shutter speed is what causes the display to be difficult to photograph, but in person it's easy to read with no issues.

I bought this to show my lathe's speed. It worked well. A little problem mounting the magnet. Instructions say south pole. I used a magnetic navigational compass to determine north/south of the provided magnet. When I mounted south pole toward the sensor, it didn't work. Turned it around and it did. I epoxied the magnet so unmounting was a nuisance. Connection was simple, just be sure to follow instruction on wire colors. Ground yourself when handling electronics to keep static zero.

I'm using it on a metal lathe. It's worked fine for several years now.

This is a nice tachometer and I’d give it 5 stars except the instructions state the “South Pole of the magnet is valid” (what that means is the South Pole faces the sensor) and they don’t mark the magnet as to poles. I know how to figure that out but it’d be nice if they labeled that.

These work well. I put one on my drill press and one on my lathe. My only complaint is that the unit should have a separate connector for the sensor and one for power. Having to splice wires to connect the sensor is so last century.

Hello All! I purchased this tachometer to provide RPM information on my drill press. After reading several reviews, I thought I would do some additional measurements of the sensor for others to use in their decision making and engineering efforts. As the sensor is a hall effect device, the magnetic polarity of the supplied magnet in relationship to the sensor DOES matter. It is essential that the SOUTH pole of the magnet face the sensor. In order to determine which side of the magnet is the south pole, I used a smart phone app provided by K&J Magnetics called KJ Pole ID (iPhone version). Simply open the app and point the top of the phone towards one face of the magnet. The app will display the magnetic polarity that is currently facing the phone. Arrange the magnet such that the app displays "The SOUTH pole of the magnet is facing the phone", then mark the face of the magnet for easy identification prior to mounting. When power to the sensor is ON and no magnet is present, the sensor will output 0VDC as shown in the picture. The red LED on the bottom of the sensor will also be illuminated. When the magnetic SOUTH pole of the magnet approaches the sensor (in my test, about a quarter inch), the red LED will turn off and the output of the sensor will switch to a positive DC voltage. In my test, this voltage is proportional to the supplied DC input voltage to the sensor minus approximately 560mV (Vout_sensor = Vdc_sensor - .560). The rise time of the sensor, or the time it takes for the output of the sensor to rise from 10 percent to 90 percent of its steady value (Vout_sensor), is 114uS. This is with a 9VDC regulated DC power supply into the sensor. Please see the attached photo for additional details. The fall time (no photo attached), is much faster with a time of 160nS. During the wiring portion of the assembly, it's important to note the colorings of the wires at the display and at the sensor. The sensor color codes are as follows: Brown: +DC supply voltage Blue: GND Black: Sensor Output Voltage (I called this Vout_sensor in my discussion above) The tachometer display color codes are as follows: Red: +DC supply voltage Black: GND Yellow: Sensor Input Voltage (Connect this lead to the Black lead of the sensor wiring) As mentioned by Digiten, the DC supply voltage must fall into the range of 8VDC to 15VDC (Do NOT use an AC-output power supply). As an engineer, this implies that any supply voltage below or above this range can cause unexpected operation or failure of the product. My recommendation is to use a walwart-style (plug in) regulated DC power supply with an output voltage of either 9VDC or 12VDC. When connecting the power supply to the tachometer, make certain that the output polarity of the power supply correlates to the input polarity of the tachometer. When mounting your display, I would recommend measuring the actual dimensions of your display first as mine were slightly different from the recommended cutout dimensions shown on the product page. The cutout portion of my display (the area behind the front mounting flange) measured 33.33mm by 68.26mm. The panel cutout dimension on the page has this listed at: 68x33mm. Those extra thousandths of an inch could make mounting the display a challenge depending on the supporting material. In my next review, I will compare the RPM values from this tachometer to the RPM values calculated from a high-end encoder and RPM measuring device :) In summary, this is a well made and nicely constructed tachometer for the price!

I bought this for my Craftsman lathe. The headstock speed chart is so faded I can't read it anymore and I can't seem to find a chart that has the same belt arrangement I have. I used the indexing pin hole on the headstock housing for a bracket location after making a stud that replaced the pin. The entire install took a couple of hours and all I bought was a few set screws and socket head machine screws to do it. I also purchased a 9 volt battery adapter container with a switch to power it from Amazon. The readout is housed in a plastic container with a lid with a gasket to protect it from the elements. I bought that at Dollar Tree for you guessed it, a dollar. The wiring diagram is simple and I used tiny wire nuts I may later solder the connections and use heat shrink tubing to seal them. Once I located where the magnet should be I marked the chuck and degreased the spot and reinstalled the magnet with the correct polarity after placing a large drop of Super Glue on the spot just in case I accidentally move the magnet. The next day it was very secure. I ran the lathe without any glue on the magnet and it never moved but I decided to anchor it better in case I knocked it off. I ran the lathe and if my chart is right on the lathe from one of the belt arrangements that I can read it is within fifteen rpm's of the chart. Chart reads 685 and digital read 700. I'm not positive the pulleys are the original ones from Craftsman but I trust the digital.

I found the tachometer easy to install and connect to its sensor. In general, it gives me a good idea of the speed. However, the display jumps around constantly and never settles down to a single reading. It strikes me that a bit more signal processing and this would be completely cleaned up. I wish I'd had the option to pay a little more and get smarter electronics.

中古の籾摺り機を購入しましたが、回転計が壊れたため、交換用に購入しました。 回転表示部は、ほぼ同じ大きさで四隅をやすりで少し削るだけで簡単に取付ができました。 センサー部は、配線が短く細いため、既存の配線と接続に手間取りましたが、何とか取付できました。

Ho acquistato questo contagiri per completare la mia fresa a controllo numerico. occorre fare attenzione ai collegamenti del sensore di hall perché se alimentato al contrario si brucia. Il magnete in dotazione non è particolarmente potente, volendo una distanza di misura di 5 o 6 millimetri ho usato al suo posto un N50 rettangolare 10x5 mm. Attenzione al fissaggio perché un magnetino da un grammo se messo in rotazione a 10000 giri produce una forza centrifuga di diverse centinaia di grammi e schizza via e può far male.

Good product. Works well and appears very accurate

Dies ist schon der zweite Tacho, den ich in meine Maschinen eingebaut habe, lief alles bisher sehr gut.Die Spannung zur Versorgung ist so variabel, daß sie mit der Ausgangsspannung meiner 2 VFDs (Lenze und Parker) ohne Probleme betrieben werden kann. Der Anschluss ist denkbar simpel. Bei dem Sensor muss man nur drauf achten, daß der Magnet recht direkt am Sensor vorbeizieht (max 1mm). Ein stärkerer Neodyn-Magnet hat da bei der kleinen Maschine geholfen, auf der grösseren ist der Radius der Welle grösser, und man kann den Magneten besser positionieren. Ich wollte keine 4 Wochen warten, deswegen die deutsche Bestellung, 4 Tage sind OK, dafür gebe ich gerne etwas mehr aus.

Great product to add to your equipment like lathe or mill or drill.