The latest articles on DEV Community by autotrue (@autotrue). https://dev.to/autotrue https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4184066%2Fc40565c2-8711-4730-aa2f-1e972e4efd94.png https://dev.to/autotrue en autotrue Wed, 14 Oct 2026 08:03:59 +0000 https://dev.to/autotrue/the-limits-i-keep-to-with-a-manual-range-car-multimeter-50hm https://dev.to/autotrue/the-limits-i-keep-to-with-a-manual-range-car-multimeter-50hm <p>A meter that reads wrongly is worse than no meter, because I'll believe it. If a number on my UT107+ doesn't make sense, my own setup is the first suspect, and the car waits until I've ruled it out. Below is the order I check things in, followed by the figures I treat as fixed and a short care routine.</p> <h2> When a reading makes no sense </h2> <p>My checks run in this order:</p> <ul> <li>Is the rotary switch on the right function? With manual ranging, choosing it is my job.</li> <li>Is the range sensible? With manual ranging, I'm the one choosing the range, so I check it before I trust the figure.</li> <li>Is the black lead in COM? It should always be.</li> <li>Is the red lead in the jack that matches the function? VΩ for voltage, resistance, frequency, temperature, RPM and dwell; mA for the 12 V battery test; 20 A only for high current.</li> <li>Are the AAA batteries still healthy? Two of them sit in the rear compartment, and I'd rather swap them than trust a doubtful display.</li> </ul> <h2> RPM or dwell looks odd </h2> <p>For RPM I check that I short-pressed SEL/VFC and picked the right engine type, 2-stroke or 4-stroke. If I've picked the wrong one, the reading isn't one I can use. For dwell I confirm the cylinder count is within what the meter handles, which is 1–8 cylinders.</p> <h2> Hard limits </h2> <p>These are the figures I don't argue with.</p> <ul> <li>High current: the 20 A jack is rated at 20 A for 10 seconds maximum. I keep high-current readings short and never leave the leads connected while I go and look at something else.</li> <li>Category: CAT II 1000 V / CAT III 600 V. I treat that as the ceiling and stay well inside it.</li> <li>Temperature: the meter's quoted range is −40 ℃ to 1000 ℃, and I measure with the supplied K-type probe.</li> <li>Leads: if the insulation on a test lead is nicked or cracked, the lead is retired.</li> </ul> <p>I also won't change the rotary switch with the probes still on a live circuit. I take them off, turn the switch, then reconnect.</p> <h2> Looking after it </h2> <ol> <li>Switch it off before packing up.</li> <li>Unplug both leads from the jacks.</li> <li>Wipe off any oil or grime picked up in the engine bay.</li> <li>Coil the leads loosely and put everything in the carrying bag, the K-type probe included.</li> <li>Keep the English manual with it, since the test-specific lead positions are easy to forget.</li> <li>If the meter is going to sit unused for a long stretch, take out the two AAA cells.</li> </ol> <p>None of this takes long, and it means I start each job from the same routine.</p> <p>Anyone curious about the meter behind these notes can find it at <a href="https://autotrue.co.uk/" rel="noopener noreferrer">autotrue.co.uk</a>.</p> hardware tools