Digital Caliper Battery Cover Switch




I'm an Engineer. I like hiking, flea markets, and electronics.

Cheap digital calipers can be bought almost anywhere, they might not be as nice or accurate as Mitutoyo calipers, but if they're a good value, what's not to love? The battery life. These things drain the battery even when you press the off button. This instructable will show how to modify the battery cover so that it acts like a switch, so that the battery can be physically disconnected from the circuit.


  1. Digital Caliper
  2. Scissors
  3. Tweezers


  1. Copper Tape

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Step 1: Add Conductive Tape to Cover

The battery cover slides much like a switch, but is non-conductive. To make it act like a switch, copper tape is placed under the cover so that it touches the top of the battery. It extends from the under-side of the cover around the side and over the top, slightly.

  1. Place conductive copper tape under the battery cover.
  2. Wrap the tape over to the top of the cover.

Step 2: Add Conductive Tape to Caliper

The sliding contact on the lid needs to make contact with another piece of conductive tape to complete the circuit. In this step, complete the path by using another piece of conductive tape to route the battery housing's side contact to a position where the battery cover's contact will touch.

  1. Trim conductive tape into a point.
  2. Position tape behind battery housing's side contact.
  3. Bend tape into position with tweezers .
  4. Trim until contact wraps around battery housing's edge.

Step 3: Insulate and Place Battery

Before placing the battery back into the housing, isolate the battery from the side-contact by placing the conductive tape's non-stick backing in front of the battery housing's side-contacts. This will keep the circuit from being completed unless the battery cover is on.

  1. Place conductive tape's backing material into battery housing in front of side contacts.
  2. Place battery into battery housing.

Step 4: Done

In this step, use the caliper.

  1. In the first picture, there is a small gap between the two copper contacts because the battery cover is slightly off so the caliper is also powered off.
  2. In the second picture, the cover is slid fully on, so there is no longer a gap between the two copper contacts. The caliper is powered on.

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    11 Discussions


    2 years ago

    I like this. I've been using this: but it's kind of finicky.


    2 years ago

    Interesting alternative. I've had the same problem, and my solution was to zip tie an AAA battery to the back of the vernier. Tack solder wires to the battery. Wires go to the data port. Negative is closest the jaws, positive furthest from the jaws.

    I've several verniers modified this way, with several years of life from the AAA battery and counting. (use a fresh battery, they like a tad over 1.5V)

    Turning the vernier off doesn't help, most power seems to go to tracking the position. Blanking the display saves only a few percent of the vernier power.

    Disconnecting the battery as done here addresses that. As long as you remember to switch off the battery case, and zero the vernier when turning it back on. Unfortunately I tend to leave verniers on sometimes....

    A new AA

    Alex in NZ

    2 years ago

    This is brilliant! The battery in my callipers fits really tightly, so removing it is such a pain that I just live with the replacement cycle. Such an elegant and simple solution to the problem. Thank you :-)

    1 reply

    2 years ago

    there is also a data port directly above the battery port. wires can be soldered to a AAA battery for cheaper replacements.

    1 reply

    Reply 2 years ago

    Good find, I saw the little cover for the data port, but didn't know it could be used to apply power. How did you discover the pinout of this port?


    2 years ago

    Excellent and elegant. I'll definitely be doing this!

    1 reply

    2 years ago

    Have you checked to see how long the battery lasted doing this. I go through batteries like candy presently and started taking the battery out when not used.

    1 reply

    Reply 2 years ago

    I was lucky if I could get a month out of a battery, so like you, I've had to keep the battery out when not using the caliper.