LED IV and light output characterisation

IV curve

Light output

Connection diagram

Wiring the photodiode to the Ext connector

Code

#!/usr/bin/env python3
# Filename: measure-led-response.py

import sys
import serial
import libStrix
import time

com = serial.Serial( sys.argv[1], 460800, timeout = 2.5 )


smu = libStrix.Strix( com, 1 )

smu.write( libStrix.PARAM_AUTORANGING, libStrix.AUTORANGING_ON )
smu.write( libStrix.PARAM_AVERAGES, 5 )

# EXT is always fixed range, 64x -> ±35mV
smu.write( libStrix.PARAM_EXT_VOLTAGE_GAIN, 64 )


# Resistance parallel to photodiode in this example
Rpd = 38e3

v_start = 0.0
v_stop = 2.61
dV = 0.01

v_current = v_start

smu.enable_output( True )

N = 0
while v_current < v_stop:
    smu.set_drive_voltage( v_current )
    time.sleep(0.1)
    Imeas = smu.measure_current()
    Vmeas = smu.measure_voltage()
    Vext = smu.measure_ext()
    Iext = Vext / Rpd

    print( N, Vmeas, Imeas, Iext )
    print( N, v_current, Imeas, Iext, file = sys.stderr )
        

    v_current += dV
    N += 1

smu.enable_output( False )

# py measure-led-response.py COMx > led-response.dat

Comparison, red vs white LED light output