This guide is using a Bosch PLR50C as an example, but the same also applies similary to any other device. You can check this list whether your device is supported. If the device is not included in the list, please send a small note to firstname.lastname@example.org so that we are aware of this. However, even if the device is not listed, it may still work. You may have to manually select a fitting Bluetooth protocol, though.
First, we should make sure that no other app is connected to the laser distance meter. Since the distance meter can only be connected to one application, an existing connection will block any further connection requests. On most laser distance meters, a Bluetooth icon indicates whether the device is currently connected or not.
If you have another app running in the background (e.g. the vendor's app), it may continuously
try to reconnect to the distance meter. Even when this is happening infrequently, like every
couple of minutes, it may disturb a reliable connection process.
In this case, you should stop the other app by
opening the Android settings and choosing 'Apps' →
Open the ImageMeter settings on the main screen. Scroll down to the Bluetooth section. Select the first item 'Laser distance meter'. A screen appears that lists all known Bluetooth devices. If your distance meter is in this list, select it. If it is not in the list, turn on Bluetooth on the distance meter and click on 'Start Bluetooth Device Scan'. Now your distance meter should appear in the list.
If you are running Android 6.0 or later, the app will ask you for the location permission to carry out the scan. This may sound strange, but is a requirement of Android 6.0 and later (as knowing the near Bluetooth device IDs may give some hints at the phone's location). You can remove the location permission for ImageMeter again after the Bluetooth device has been configured.
On some devices, the distance meter name does not show (i.e., only its Bluetooth address appears). ImageMeter can still use the device, but you will have to select the Bluetooth protocol manually in this case. If your measuring device is a classic Bluetooth device (you can check in this list), you can pair the devices manually in the Android Bluetooth settings. It should then appear in the ImageMeter settings as a known device with correct name. However, if your laser distance meter is a Bluetooth LE device, no pairing is required. It is even not advised to pair LE devices, because some phones will then register the measuring device as an external keyboard, which cannot be removed easily (often requires a reboot).
Now, back on the main screen of ImageMeter, click on the Bluetooth icon. It will start to blink, indicating that it is now trying to connect to the distance meter. If this is a 'classic Bluetooth' device and this is the first connection between the two devices, ImageMeter will start a pairing request. When the connection is successfully established, the icon will turn blue and we are ready to go. If it does not work, check again that there is no other app blocking the connection and that the correct device was selected in the settings. In very rare cases, you may need to restart the distance meter or your Android device.
With the laser distance meter connected to ImageMeter (blue Bluetooth icon), open an image to enter the editor. Values transmitted over Bluetooth are always copied to the active measure. Hence, either draw a new measure or select an existing measure. When you now carry out a measurement on the distance meter, it will appear automatically at the selected measure. On some devices (e.g. Leica D3aBT), you have to explicitly press the Bluetooth button on the distance meter to transmit the value.
Some laser distance meters transmit not only the distance value itself, but also the currently selected unit. In this case, ImageMeter can either use the same unit as on the distance meter, or the number format specified in ImageMeter. This can be selected in the ImageMeter settings, section 'Bluetooth → Use device value format'.
Depending on the distance meter model, and the mode it operates in, it will not only transmit lengths, but also angles or areas. If these are transmitted, they can also be received by ImageMeter. Which value will be received depends on the measure selected in ImageMeter. For example, a device might always transmit a length and the angle, at which it was taken, together. When a length measure is active in ImageMeter, the length part will be received, and when an angle measure is active, the angle will be received, respectively.
Some drawing elements need more than two measurements. For example, the perspective reference needs one for its horizontal side and one for the vertical side length. In this case, you can click on the dimension label to select it. The Bluetooth measurement will then be set to the selected label. The label selection will automatically advance to the next label after receiving a value over Bluetooth.