Teardown Tuesday: Digital Tape Measure

Introduction

The eTape16 digital tape measure. Image courtesy of Amazon.

A lot of people have trouble reading tape measures. In an effort to make life easier, there are digital tape measures that simply show you the distance on a screen. In this Teardown Tuesday, we are going to take a look at one of these digital tape measures.
This tape measure has quite a few features such as the ability to display measurements in several different units. The particular tape measure used in this teardown is an eTape16 purchased from Amazon for around $30.

Opening it Up

Compared to last week’s teardown, this one was a breeze! Several Phillips screws held this plastic enclosure together. They were easily removed and the enclosure simply pulled apart. The tape measure component had a spring that was wound up and, upon opening, it rapidly ‘unsprung’.

The exposed electronics

The Circuit Board

The primary PCB

There is a primary circuit board that contains most of the electronics inside of this digital tape measure. This PCB measure approximately 63mm by 59mm and is only populated on a single side with surface mount components. This two-layer board measures 1.27mm thick and it has white silkscreen on both sides of it. The circuit board inside of this tape measure is quite barren compared to some of the other teardowns.

The display PCB

There is second minor PCB inside the tape measure that contains the display and two small push buttons. This is a single-layer board that measures 58mm by 24mm. This is board connects to the primary PCB through a polyamide cable with 25 circuits. The display on this digital calculator is a segmented LCD with many segments. This display is connected to the PCB through 22 pins. The digital aspect of this tape measure has a resolution of 0.1mm.

Microcontroller

This tape measure has an 8-bit microcontroller that runs all of the functions the tape measure offers. This is manufactured by ABOV Semiconductor, part number MC96F6432Q. This is based on an 8051 core and has a lot of peripherals incorporated inside of it. For example, this microcontroller has an LCD driver and step down regulator built in. Take a look at the full datasheet here.

The ABOV microcontroller

Sensors

The PCB component of the encoder

There are two sensors on this tape measure used to determine the position of the tape measure: an encoder and an optical sensor. The encoder is comprised of exposed pads on the rear of the primary PCB (seen above) and fingers on the tape reel mechanism (seen below).

The finger component of the encoder

In addition to the encoder, there is an optical sensor that reads markings off of the tape measure. Through the entire 16 feet, there are black barcode-like markings on down the middle of it.

The optical sensor and barcoded tape

Wrapping It Up

As you can see from this teardown, this is not an industrial device. Its lack of shock proofing, water resistance, and ruggedness confirm that it's aimed at the consumer market.
Below is a video of this tape measure in action.