Python class for remote controlling EastTester ET54 series electronic loads.
Should work with ET5410, ET5411, ET5420, ET5410A+, ET5411A+, ET5420A+, ET5406A+, ET5407A+
"Works on my machine" (ET5410A+, LINUX). Needs a lot more real world testing:
- in actual circuits (does the load realy do what I think?)
- with all the different models of the series
- on Windows and MacOS
Most modes of operation and all measurements have been implemented:
| Feature | Status |
|---|---|
| Input on/off | ✓ |
| Voltage and current ranges | ✓ |
| OCP, OVP, OPP | ✓ |
| Trigger support | ✓ |
| V/A/P/R readout | ✓ |
| CC mode | ✓ |
| CV mode | ✓ |
| CP mode | ✓ |
| CR mode | ✓ |
| CC+CV mode | ✓ |
| CC+CR mode | ✓ |
| Short mode | ✓ |
| LED mode | ✓ |
| Battery mode | ✓ |
| Transient mode | ✓ |
| List mode | ✓ |
| SCAN mode | (✓) |
| Qualification test mode | ✓ |
| Load effect testing | — |
| File commands | — |
| System setup | — |
Here is a little example script that illustrates how things work:
#!/bin/env python3
import time, datetime
from ET54 import ET54
# connect to the load
el = ET54("ASRL/dev/ttyUSB1::INSTR")
# set ranges
el.ch1.Vrange = "high"
el.ch1.Crange = "high"
# set protections
el.ch1.OVP = 24.5
el.ch1.OCP = 4
el.ch1.OPP = 85
# start in constant current mode (3.1A)
el.ch1.CC_mode(3.1)
el.ch1.on()
# switch to CCCV mode
el.ch1.CCCV_mode(2.5, 13.5)
# and change the current on the way
el.ch1.CCCV.current = 1.25
# monitor voltage, current, power and resistance for a minute
print("timestamp, V, I, P, R")
for i in range(60):
print(", ".join([str(x) for x in [
datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
el.ch1.read_voltage(),
el.ch1.read_current(),
el.ch1.read_power(),
el.ch1.read_resistance(),
]]))
time.sleep(1)
# turn off the load channel
el.ch1.off()
- SCAN mode is implemented but I don't understand, how to retrieve the result of the comparison.
- Sometimes, the instrument takes a long time to respond which makes some tests
fail randomly (typically
LIST_mode). - During
BATT_modetests, the device display looks weird at times. - Display shows weird numbers when setting
TRANSIENT_widthvalues.
Some of these may be firmware quirks, others are probably my fault.
- Download the latest release package (
et54-XXX.tar.gz) from github. - If you want to install in a virtual environment, first, create and activate it:
python -m venv .venv
source .venv/bin/activate
- Install the package (replace XXX with the correct number)
python -m pip install et54-XXX.tar.gz
The following sections give a tour of available functionality. Detailed
api-documentation is given in the doc-strings of the classes. Use pydoc to
access it:
python -m pydoc ET54
python -m pydoc ET54.instrument
python -m pydoc ET54.channel
For questions about valid values for all commands and general use of the device, please refer to the manufacturers user manual and/or scpi manual.
This is how you connect to the load:
from ET54 import ET54
el = ET54("ASRL/dev/ttyUSB1::INSTR")
Or, on windows:
from ET54 import ET54
el = ET54("ASRL2::INSTR")
Of course, you need to adapt it to the right device for your case. See here for details on pyvisa resource names.
The instrument instance provides the following methods.
# sound a beep
el.beep()
# reset to default
el.reset()
# unlock the keypad
# usually not advisable!
el.unlock()
# the next command will automatically lock again
# send trigger event
el.trigger()
# query fan state
el.fan()
# Write SCPI command to connection and check status
# e.g. set channel 1 CV mode voltage setting to 12.5V
el.query("VOLT1:CV 12.5")
# Write SCPI command to connection and return answer value
# e.g. query channel 1 CV mode voltage setting
el.query("VOLT1:CV?")
# print device and status information
print(el)
The instrument object has one or two channel, depending on your model. Channel
objects can be accessed directly (el.ch1, el.ch2) or from the
channel list (el.Channels[0]).
Each channel provides lots of attributes and methods for configuring different modes of operation, measuring etc. All parameters that are part of the configuration object attributes and can be read and set just like any other Python variable:
my_OCP_value = el.ch1.OCP
el.ch1.ocp = 12.8
There are a few exceptions that are read-only.
Measurements, on the other hand, are represented as functions (methods) that return a measurement value when called. E.g.
el.ch1.read_current()
Obviously, these cannot be set.
# Turn input on/off
el.ch1.on()
el.ch1.off()
# or
el.ch1.input = "ON"
el.ch1.input = "OFF"
# query input state
print(el.ch1.input)
# set manual trigger (*Trg* button on keypad)
el.ch1.trigger_mode = "MAN"
# set external trigger (connector at back of the instrument)
el.ch1.trigger_mode = "EXT"
# set software trigger (`el.trigger()`)
el.ch1.trigger_mode = "TRG"
The load provides configurable protection against over-current, over-voltage and over-power. They can be set like this:
el.ch1.OVP = 12.5
el.ch1.OCP = 3.2
el.ch1.OPP = 35
The values can also be queried:
>>> el.ch1.OVP
155.0
>>> el.ch1.OCP
42.0
Query the state of all protections (including no-configurable over-temperature and reverse-polarity protection):
>>> el.ch1.protection
'NONE'
There are two different ways to configure a mode:
- Use the
modemethod and set all parameters separately - Use Individual
XXX_modeconfiguration methods that take all parameters as arguments.
Example: configure CC mode
el.ch1.CC_current = 2.5
el.ch1.mode = "CC"
or
el.ch1.CC_mode(2.5)
Both will have the same effect. Both allow changing any parameter after setup.
Short circuit mode takes no parameters.
el.ch1.SHORT_mode()
These modes take a single parameter that defines the desired current, voltage, ...
# 3 A constant current
el.ch1.CC_mode(3)
# 12.5V constant voltage
el.ch1.CV_mode(12.5)
# 100 Ohm constant resistance
el.ch1.CR_mode(100)
# 50W constant power
el.ch1.CP_mode(50)
Or set them up sequentially:
# 3 A constant current
el.ch1.CC_current = 3
el.ch1.mode = "CC"
# 12.5V constant voltage
el.ch1.CV_voltage = 12.5
el.ch1.mode = "CV"
# 100 Ohm constant resistance
el.ch1.CR_resistance = 100
el.ch1.mode = "CR"
# 50W constant power
el.ch1.CP_power = 50
el.ch1.mode = "CP"
As the name suggests, these modes combine two of the basic modes and require two parameters.
# 2.0A, 12.5V in CC+CV mode
# all of these are equivalent:
el.ch1.CCCV(2, 12.5)
el.ch1.CCCV(current=2, voltage=12.5)
el.ch1.CCCV(voltage=12.5, current=2)
# CRCV 100 Ohm, 13.5V
# all of these are equivalent:
el.ch1.CRCV(100, 13.5)
el.ch1.CRCV(resistance=100, voltage=13.5)
LED simulation mode is defined by three parameters:
- Current
- Voltage
- Coefficient
el.ch1.LED_mode(V=8.1, I=0.8, coef=0.5)
or
el.ch1.LED_voltage = 8.1
el.ch1.LED_current = 0.8
el.ch1.LED_coeff = 0.5
el.ch1.mode = "LED"
XXX: write me
el.ch1.BATT_mode(mode, value, cutoff, cutoff_value)
XXX: write me
el.ch1.TRANSIENT_mode(mode, trigmode, value, width)
XXX: write me
el.ch1.LIST_mode(stepmode, params)
XXX: write me
el.ch1.SCAN_mode(mode, threshold, threshold_value, compare, limits, start_end, step, step_time)
XXX: write me
el.ch1.QUALI_mode(Vrange, Crange, Prange)
XXX – not implemented, yet
Once the load is set up, you can start reading measurement data
from it. In contrast to parameters, measurements are implemented as read_
methods. There are four quantities you can measure:
V = el.ch1.read_voltage()
I = el.ch1.read_current()
P = el.ch1.read_power()
R = el.ch1.read_resistance()
The SCPI implementation in the instrument is a bit wonky. I spent a lot of time figuring out some peculiarities and have managed to fully crash the controller many times. Many of these problems had to do with timing (some commands are fast, others require some time before you may send a new command). The SCPI documentation by the manufacturer is a bit obscure and incomplete in some places.
It is quite possible that different models and/or firmware or hardware revisions behave slightly different than my instrument. If you encounter problems, you can try tweaking a few parameters:
| parameter | Description |
|---|---|
baudrate |
must match baudrate set in device (default: 9600) |
eol_r |
line terminator for reading from device (default: "\r\n") |
eol_w |
line terminator for writing to device (default: "\n") |
delay |
delay after read/write operation [s] (default: 0.2) |
timeout |
timeout [ms] before giving up on read requests (default: 1000) |
model |
model ID [ET5410/ET5420/ET541A+/...] only required if *IDN? does not return a valid ID e.g. for Mustool branded ET5410A+ |
The most likely candidate to fix weird problems is delay. The device manual
does not specify what command frequency or processing time the instrument has
so I used the smallest value that allowed all my test cases to pass. I also
asked ET support about it and the answer was "The time interval should be above
200ms" which matches my own observations, but your mileage may vary.
Example:
el = ET54("ASRL/dev/ttyUSB0", delay=0.5, baudrate=14400)
If you want to play with the device on raw metal and try some SCPI commands yourself, you can connect to it like so
tio -e -b 9600 -m INLCRNL,OCRNL /dev/ttyUSB0
You can use other programs like minicom etc. Just make sure to get the weirdly inconsistent line terminators right.
Caution: The device uses an internal usb2serial device (QinHeng Electronics CH340 serial converter) which is detected by the operation system even if the load is turned off. There is nothing I can do about that. Obviously, you cannot talk to the device in that state.
There are Mustool branded versions of the ET5410A+ and possibly also of the
other models. These devices run a modified firmware and return an unhelpful
model ID (xxxxxx) in response to the *IDN? SCPI command. To make these
devices work, you need to explicitly provide the model ID when initializing the
device:
from ET54 import ET54
el = ET54("ASRL/dev/ttyUSB0", model="ET5410A+")
If you think you found a bug or you have an idea for a new feature, please open an issue here on GitHub. Please do not submit pull-requests before discussing the issue you want to address.
If you want to report a bug, please make sure to replicate the erroneous behavior at least once before opening an issue and provide all information necessary to replicate the problem (what commands did you use, what was connected to the load, what did you observe, what did you expect?).
I would very much appreciate help from people who own any of the various models listed above: It would be great if they could run the automated tests on their devices and let me know if that went fine or produced errors. Please get in touch if you would like to do that. Also any feedback and bug reports are welcome.