dmm.js-serial v1.2.0
DMM.js
Node.js RS232 API for compatible DMM (Digital Multimeter) and other SCPI-compatible devices.
Storytime section: I got a spare Agilent 34401A DMM at home, but the display is not working properly (some segments are faulty). I decided to perform readings through the serial port, but I cannot find any suitable library or tool under unix / macOS, so I decided to make my own one.
Installation
npm i dmm.js-serialQuick usage
const DMMjs = require('dmm.js-serial');
const my34401a = new DMMjs('/dev/tty.usbserial');
(async () => {
await my34401.open();
await my34401.linkDevice();
let info = my34401.getDeviceInfo();
console.log('Got device:', info.id, '( version', info.version, ')');
let vMeas = await my34401.readDCVoltage();
console.log('Read', vMeas, 'V');
// Got device: HEWLETT-PACKARD,34401A ( version 1998.0 )
// Read 10.6414 V
});Examples
Check the examples folder and try the available scripts!
connectwill link, read device id and version, unlinkerrorsproduces some errors, then reads the result codesreadperform DC & AC voltage and current measurement, plus resistance (2W) and frequencyselftestruns the device selftest and returns the pass/fail statusterminalsreads the current terminals position, wait for the user to switch it, displays new valuetextwill play with the display function and show some messages
RS232 setup
This library is based on the famous serialport package and will inherit some of its config properties. After many hours, I finally found a working configuration for it so the communication can be established between the device and my laptop, but if you have issues on your side, you can pass different setting values during the DMM initialisation:
const customConfig = {
rxTimeout: 10000, // timeout (ms) for the read command
txPause: 500, // delay (ms) to wait after a command
// serialport library config
baudRate: 9600,
stopBits: 2,
dataBits: 8,
parity: "none",
rtscts: true,
xon: true,
xoff: true,
xany: true,
// hardware flow config
flowControl: {
dsr: true,
dtr: true,
cts: true,
brk: false,
rts: false
}
};
const myDevice = new DMMjs('/dev/serial123', customConfig);Most of the time, you'll just have to change the baudRate and parity values. Under Agilent / Keysight / HP devices, you can see the current setting value under:
[MENU] > [E: I/O] > 3: BAUD RATE
[MENU] > [E: I/O] > 4: PARITY
[MENU] > [E: I/O] > 5: LANGUAGE (ensure SCPI is set)API
Opening the serial port connection
myDevice.open()Link device
Will set the device in remote mode (if not already), and reset / clear instrument state if the keepState property is set to false.
myDevice.linkDevice(keepState)Unlink device
Will set the device in local mode.
myDevice.unlinkDevice(keepState)Closing the serial port connection
myDevice.close(keepState)Get device information
Must be done once the device has been linked.
myDevice.getDeviceInfo()Display text on the DMM's screen
Depending of your device, text might be truncated
setDisplayText("Hello DMM!")Clear display text
clearDisplayText()Enable / disable device display
setDisplayVisibility(isON)Run device selftest
Returns 0 if "PASS", -1 or -2 if failed
selfTest()Get terminals position
Returns "front" or "back" depending of the terminals switch position
getTerminalsPosition()Get device errors
Returns an object with the code id and error message.
Run it multiple time to read and flush all the errors.
getErrors()Reset device
Only the clearDeviceStatus will clear the pending error buffer
resetDevice()
clearDeviceStatus()Perform DMM measurements
Each value is returned as a float object, mesurements are done using the CONF ... AUTO, and then READ? commands. No range or trigger is set (immediate reading).
readDCVoltage()
readACVoltage()
readDCCurrent()
readACCurrent()
readResistance()
readFrequency()Please note that the readResistance method only uses two wires. For the 4T sensing (Kelvin mode), you'll need to use readCommand with CONFigure:FRESistance SCPI command.
Write commands to DMM
Command must be a SCPI-compatible string (refer to the Documentation section below)
After each write command operation, a delay is applied (see txPause in the config object)
writeCommand(command)Read commands from DMM
Command must be a SCPI-compatible string (refer to the Documentation section below)
If timeout is set (in ms), it overrides the default rxTimeout from the config object.
readCommand(command, timeout)Debugging
Verbose can be enabled by setting the given property when passing the configuration file for the device instance:
const myDevice = new DMMjs('/dev/serial123', {verbose: true});This will log all commands and raw response strings shared between the device and the library.