{"id":3553,"date":"2026-10-09T08:13:07","date_gmt":"2026-10-09T00:13:07","guid":{"rendered":"http:\/\/www.edu2day.com\/blog\/?p=3553"},"modified":"2026-10-09T08:13:07","modified_gmt":"2026-10-09T00:13:07","slug":"how-to-measure-the-speed-of-a-dc-brush-square-gear-motor-46e1-33bc86","status":"publish","type":"post","link":"http:\/\/www.edu2day.com\/blog\/2026\/10\/09\/how-to-measure-the-speed-of-a-dc-brush-square-gear-motor-46e1-33bc86\/","title":{"rendered":"How to measure the speed of a DC Brush Square Gear Motor?"},"content":{"rendered":"

As a supplier of DC Brush Square Gear Motors, I\u2019ve spent the last seven years walking alongside original equipment manufacturers (OEMs) and small-batch builders who come to me scratching their heads about motor speed measurement. More times than I can count, a customer will share a story like this: they\u2019ve installed our gear motor in a conveyor system for small parts, watched it run for a week, then noticed their parts are being fed too fast, but when they use a cheap multimeter\u2019s RPM reading, it\u2019s off by 150 RPM\u2014and they can\u2019t figure out if that\u2019s a problem with the motor, their setup, or their measurement tool. That\u2019s why I\u2019m putting this together today, not as some textbook-length tutorial, but as the hard-won advice I\u2019ve picked up from troubleshooting thousands of these exact scenarios. DC Brush Square Gear Motor<\/a><\/p>\n

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The first thing I tell every new customer is: DC Brush Square Gear Motors aren\u2019t the same as the tiny brushed motors you\u2019d find in a toy car. Their square gear housing is designed for torque, not just speed, and adding that gear train adds friction, mechanical play, and even small variations in gear tooth engagement that make a one-size-fits-all measurement trick useless. When someone asks me \u201chow fast is this motor actually running?\u201d I never just point to the nameplate\u2014because nameplate RPM is a ideal number, measured in a lab with no load and perfectly calibrated power. Real-world speed? That\u2019s a moving target, and measuring it correctly requires matching your method to what you\u2019re using the motor for.<\/p>\n

Let\u2019s start with the most common mistake I see: using a contact-based tachometer. I once had a customer reach out panicking because their conveyor motor was showing 200 RPM on a dial tach they\u2019d picked up at a hardware store, but their batch of parts was piling up. I drove an hour to their shop (that\u2019s the perk of being a local supplier for midwest OEMs, by the way) and watched them press the tach\u2019s small rubber tip to the gear shaft\u2014every time they did that, the tach would dip by 50 RPM, because the friction from the tip was dragging down the motor. For low-torque square gear motors, that contact method is about as reliable as guessing your coffee temperature by the steam. I\u2019ll concede: if you\u2019re measuring a motor under a heavy, consistent load (like a 50lb conveyor hopper), a contact tach can work if you use a low-torque adapter, but for 90% of our customers, it\u2019s more trouble than it\u2019s worth.<\/p>\n

My go-to for quick, accurate measurements when a customer is testing a motor on their bench? A non-contact optical tachometer. Here\u2019s how I teach them to do it, step by step, because I\u2019ve seen too many people apply the sticker wrong and get garbage numbers. First, you need a small reflective tape dot\u2014stick one to the output gear shaft<\/em> (not the motor\u2019s armature shaft, because that\u2019s spinning faster and the gear train\u2019s gear reduction will throw your numbers off). Wait, no\u2014wait, hold on, that\u2019s a critical detail I almost messed up with a customer last quarter. If your motor is a 100:1 gear ratio, the armature spins 100 times for every 1 time the output shaft spins, so taping the armature shaft would make your optical tach count 100 pulses per output shaft rotation, leading to a 100x overcalculation. Duh, I know, but you\u2019d be surprised how many experienced technicians miss that. So: tape a single, 10mm reflective dot to the motor\u2019s output shaft<\/em>\u2014the one that connects to your load, not the part inside the gear housing. Next, make sure your workbench is still, no fans blowing the dot around, and point the tach directly at the dot, not at the motor\u2019s housing. Hold it about 6 inches away, and press the trigger. You\u2019ll get a reading in 2 or 3 seconds, and it\u2019s almost always within 2% of the actual speed we test here in our warehouse. Pro tip: if your tach keeps flickering, use two dots 180 degrees apart\u2014this stabilizes the signal, especially with square gear motors that can have slight vibration as the gears turn.<\/p>\n

But what if you need to measure speed while the motor is under actual load<\/em>? Because here\u2019s the thing: a motor\u2019s speed drops when you add load, and if you\u2019re using it for something like a packaging machine that requires consistent fill rates, you can\u2019t measure it on a bench with no load. That\u2019s where our second most-used tool comes in: a Hall effect sensor. Hall sensors work by detecting the magnetic field from a small neodymium magnet mounted on the output shaft. The cool part is, you don\u2019t have to touch the motor or even open the gear housing (which is a big deal\u2014tampering with the square gear housing\u2019s seal voids the warranty, something I have to remind customers of at least once a month). For our DC brush square gear motors, we include a tiny, pre-calibrated magnet mount with every motor over 50W, because almost all customers end up using Hall sensors for permanent installation. The setup is simple: mount the Hall sensor 1mm away from the magnet (any closer and it\u2019ll rub, any farther and it won\u2019t pick up the signal), run the sensor\u2019s wire back to a multimeter with a frequency setting, then calculate RPM by multiplying the frequency reading by 60. For example, if the sensor reads 2 Hz, that\u2019s 2 revolutions per second, times 60 is 120 RPM. This method is perfect for real-world use, and I\u2019ve even had a customer use a cheap Arduino with a Hall sensor to build a custom speed controller that adjusts for load changes\u2014though that\u2019s a more advanced use case.<\/p>\n

Now, let\u2019s talk about the mistakes that even experienced people make. Last month, a customer from a medical device company called me in a panic because their motor was running at 320 RPM instead of the 300 they specified, and they were convinced our motors were defective. I asked what method they used to measure, and they said they used the multimeter\u2019s RPM function\u2014turns out, the cheap $20 multimeter they bought only works for AC motors, not DC brush motors. That\u2019s a huge one. A lot of entry-level multimeters have a \u201cRPM\u201d setting, but it\u2019s designed for AC household motors, not variable-speed DC motors with gear trains. Always, always, make sure your multimeter is labeled for DC motor RPM measurement, or use a separate tachometer that explicitly states it works for DC brushed motors. The other big mistake is not accounting for voltage drop. DC motors draw more current when under load, and if your power supply is undersized, the voltage will drop, which slows the motor down. I once had a customer with a custom conveyor system that was running on a 12V battery, but they\u2019d already wired a relay and two sensors into the circuit, so by the time the power got to the motor, it was only 10.8V\u2014hence the slow speed. When they swapped to a higher-capacity power supply, their speed jumped right back to the 180 RPM they needed. That\u2019s why I always recommend testing speed at the motor\u2019s input terminals<\/em>, not the outlet or the power supply\u2014any wiring or connections between the power source and motor can cause voltage loss, which skews readings.<\/p>\n

I also want to touch on a more niche scenario: if you\u2019re using our square gear motors for a high-precision application, like a laboratory pipette or a semiconductor parts handler, where speed has to be accurate within 1 RPM. For that, we recommend using a laser tachometer. These are the ones that look like a small gun, and you point the laser at any surface\u2014no tape, no magnets required. They work by detecting changes in surface texture (even the slight machining marks on the output shaft) to count rotations. We use laser tachometers in our own QA lab, and they\u2019re accurate enough to catch a gear with a slightly worn tooth that causes a 2 RPM slowdown under load, which would be unnoticeable with optical or Hall sensors. The catch? They\u2019re more expensive\u2014around $150 for a good one\u2014so most customers only invest in them when precision is non-negotiable.<\/p>\n

At the end of the day, the goal of measuring your DC Brush Square Gear Motor\u2019s speed is to make sure it\u2019s meeting your application\u2019s needs, not to hit some arbitrary number from a nameplate. Every motor we ship goes through a baseline speed test at our warehouse, so if you\u2019re getting a reading that\u2019s way off, reach out instead of second-guessing your method. I\u2019ve helped customers adjust for power supply issues, helped them mount tape or magnets correctly, and even walked them through calibrating their tachometer over the phone more times than I can count.<\/p>\n

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If you\u2019re struggling to get accurate speed readings for your current project, or if you\u2019re working on a new design and want to talk through what measurement method will work best, don\u2019t hesitate to reach out. As a supplier who\u2019s built their business on solving real problems, I\u2019m here to help\u2014whether you just need a quick question answered, or you want to walk through testing a new motor in your facility. We don\u2019t just sell motors; we partner with builders to make sure their projects run smoothly, and that starts with clear, honest advice about every part of the process, including speed measurement.<\/p>\n

BLDC Square Gear Motor<\/a> References<\/p>\n

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  1. DC Motor Speed Measurement: Best Practices for Industrial Applications, Motion Control Association, 2022<\/li>\n
  2. Hall Effect Sensor Usage for Brush Motor Speed Monitoring, IEEE Transactions on Industrial Electronics, Vol. 69, No. 4, 2022<\/li>\n
  3. Optical Tachometer Calibration for Gear Motor Testing, Journal of Mechanical Engineering Research, Vol. 15, No. 2, 2023<\/li>\n<\/ol>\n
    \n

    Hangzhou ANG Drive Co., Ltd.<\/a>
    As one of the most professional dc brush square gear motor manufacturers and suppliers in China, we’re featured by quality products and good service. Please rest assured to wholesale custom made dc brush square gear motor from our factory. Good service and quality products are available.
    Address: No.185, Jincheng Rd., Hangzhou 311202, China
    E-mail: export2@angdrive.com
    WebSite:     https:\/\/www.anjodrive.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    As a supplier of DC Brush Square Gear Motors, I\u2019ve spent the last seven years walking … How to measure the speed of a DC Brush Square Gear Motor?<\/span>Read more<\/a><\/p>\n","protected":false},"author":21,"featured_media":3553,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3516],"class_list":["post-3553","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-dc-brush-square-gear-motor-4f78-344260"],"_links":{"self":[{"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/posts\/3553","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/users\/21"}],"replies":[{"embeddable":true,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/comments?post=3553"}],"version-history":[{"count":0,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/posts\/3553\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/posts\/3553"}],"wp:attachment":[{"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/media?parent=3553"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/categories?post=3553"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.edu2day.com\/blog\/wp-json\/wp\/v2\/tags?post=3553"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}