Talking to a UNI-T UT8803E bench multimeter

This is an implementation of the data protocol used by the UNI-T UT8803E (or UT8803) bench multimeter.

Status

The software provides all functionality of the original vendor software (but without a GUI) plus a few things that are not available in the windows program. However, there are still a few status flags that seem to exist but I haven't figured out their meaning, yet.

It has been tested successfully with a UT8803E on LINUX (Debian 12).

I think it should also work on MacOS or Windows, but that is untested. If you have successfully tested it on those systems, please let me know and I'll update this statement.

I no longer own the multimeter so if you find a bug I will need your help for testing.

In a nutshell

Start logging data

ut8803e log

Log to file

ut8803e log > mydata.csv

Log for 30 seconds in JSON format

ut8803e -f json -p 0:0:30 log

Log for 1.5 hours

ut8803e -p 1:30:00 log

Get device-ID

ut8803e get_ID

Toggle hold

ut8803e hold

Change display brightness

ut8803e brightness

Installation

From the latest release file, download an installable file (ut8803e*.tar.gz or ut8803e*.whl) and install it with pip or pipx.

Prerequisites

First, you need to install the hidapi library. On a Debian system it is provided by two different libraries, so you can do:

apt install libhidapi-hidraw0

or

apt install libhidapi-libusb0

If you are on Windows, you need to download the zip file from the latest release on the hidapi repository on github and the following permission discussion does not apply. For MacOS, I have no clue. Please let me know if you do.

When plugging in the device, it will show up as /dev/usbhidraw*, be owned by root and not accessible to regular users:

$ ls -la /dev/hid*
crw------- 1 root root 241, 0 Okt 12 17:15 /dev/hidraw0

So running the program as a regular user will fail. For initial testing, you can run as root:

sudo ut8803e

But it is not recommended to do that for productive use. Instead, you need to install a udev rule file that makes the device user accessible. Create a file /etc/udev/rules.d/50-CP2110-hid.rules and put this into it:

# Make CP2110 usb hid devices user read/writeable
KERNEL=="hidraw*", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea80", MODE="0666“

Or just copy the file provided in this repository.

After re-plugging the multimeter, it should appear like this:

$ ls -la /dev/hid*
crw-rw-rw- 1 root root 241, 0 Okt 12 17:15 /dev/hidraw0

So now, regular users can read from and write to it.

Install using pipx (recommended)

The recommended way of installing is pipx. If you don't already have that, you need to install it, too:

apt install pipx

Now, you can run

pipx install ut8803e-*.tar.gz 

or

pipx install ut8803e-*.whl 

Install using pip and venv (more involved)

If you use pip, instead, you will most likely need to create a venv, first:

python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install ut8803e-*.tar.gz 

You will need to repeat the source part to activate the venv whenever you coma back and want to run the program.

Usage

This is a simple command line tool that takes exactly on argument and supports a few options:

Usage: ut8803e [OPTIONS] CMD

  Commands:

      log             start logging data

      get_ID          get instrument id

      brightness      change display brightness (3 steps)

      select          press `select` button

      range_manual    switch to next manual range

      range_auto      set auto range

      minmax          set/toggle min/max mode

      exitminmax      exit min/max mode

      rel             set relative mode

      d_val           capacitor D value

      q_val           inductance Q value

      r_val           inductance/capacitor resistance

      exit_dqr        exit DQR mode

Options:
  -p, --period TEXT       Length of logging period [HH:MM:SS]. Max period: 23:59:59
  -i, --interval INTEGER  Logging interval [s]
  -f, --format TEXT       Logging data format (csv/json/reversing)
  --full                  show value even if ERR or OL app

Most commands act the exact same way as pressing the respective button on the instrument.

Logging data is printed in to STDOUT in csv format, by default. You can also get JSON records with --format json. Finally, there is --format reversing which will log binary and hex data of the status record. This is intended for reverse engineering additional features or adding support for other models.

and can be redirected to a file using the facilities of your operation system or shell. E.g. ut8803e/py log > data.csv on LINUX.

Warnings and Debugging information are printed to STDERR.

Protocol reverse engineering

If you are interested in how I went about figuring out the communication protocol, have a look at my blog post covering that. Sorry – only in German right now.

Contributing

If you are interested to contribute, please open an issue that clearly describes the change, feature or bugfix that you would like to suggest. Please do not submit pull requests without discussing the issue first.

The UNI-T programming manual suggests that there are at least two more status flags that haven't been implemented, yet and that I do not understand:

• Series/Parallel (SER/PAL) in capacity and inductance mode. There are corresponding indicators on the LCD but I have no idea what that means.
• Over/underflow – again not sure what exactly that is supposed to be.

So if you know anything about that – get in touch.

The UNI-T documentation suggests that, with some modifications, this may work with other models, too:

• UT8802/UT8802N
• UT632/UT632N
• UT803/UT803N
• UT804/UT804N

Unfortunately, I do not have access to any of those models so I may be wrong. If you have one of them and are willing to help, please get in touch.