IEC IEC 61131-2 digital inputs.py

# ******************************************************************************
# Measurement script for 24V digital input current profiles
# Rigol DP832 & DMM7510 & Keithley 196
# https://btbm.ch/24vdc-iec-61131-2-compliant-digital-inputs-with-jelly-bean-parts/
# Copyleft 2022 Grease monkey - No rights reserved
# !!! Don't laugh at the code. I change engine oils for a living !!!
# ******************************************************************************


import vxi11
import pyvisa
import time
import math
import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
from matplotlib.collections import PatchCollection
import numpy as np

rm = pyvisa.ResourceManager()
# Rigol DP832 @ 192.168.1.108
psu = vxi11.Instrument("192.168.1.108")
# Keithley DMM7510 @ 192.168.1.50
dmm7510 = vxi11.Instrument("192.168.1.50")
# Keithley 196 @ GPIB 7
dmm196 = rm.open_resource('GPIB0::7::INSTR')


def psu_set_voltage(channel, voltage):
    if channel == 1 or channel == 2 or channel == 3:
        if 0 <= voltage <= 32:
            psu.write(":SOUR" + str(channel) + ":VOLT " + str(voltage))
        else:
            print("Invalid voltage")
            exit()
    else:
        print("Invalid channel name")
        exit()


def psu_on(channel):
    if channel == "CH1" or channel == "CH2" or channel == "CH3" or channel == "ALL":
        psu.write(":OUTP " + channel + ",ON")
    else:
        print("Invalid channel name")
        exit()


def psu_off(channel):
    if channel == "CH1" or channel == "CH2" or channel == "CH3" or channel == "ALL":
        psu.write(":OUTP " + channel + ",OFF")
    else:
        print("Invalid channel name")
        exit()


# This function reads two consecutive values from the 196
# and compares them to see if the readings have settled
# it also retries to read values if no reading was received
def dmm196_read_value(settling_time=0.0, settling_difference=0.0001):
    measurements = [1, 2]
    n = 0

    while abs(measurements[0] - measurements[1]) > settling_difference:
        measurement = float('nan')
        while math.isnan(measurement):
            try:
                time.sleep(0.01)
                measurement = float(dmm196.read())
                measurements[n] = measurement
                if n < 1:
                    n += 1
                else:
                    n = 0
            except:
                pass
        time.sleep(settling_time)
    return measurements[0]


# Number of measurements
no_of_measurements = 300
# Maximum test voltage
max_volts = 30

psu_set_voltage(2, 0)
psu_set_voltage(3, 5)
psu_on("CH2")
psu_on("CH3")
# Wait a bit till the circuit settles
time.sleep(1)

# Setup DMM7510 to measure Volts DC
dmm7510.write("FUNC \"CURR\"")
dmm7510.write(":SENS:CURR:NPLCycles MAX")

# Setup DMM196 to measure DC Voltage
# Function = F0 (Volts)
# Range = R4 (300V)
# Filter = P0 (Disabled)
# Rate = S3 (6 1/2 digits)
# Trigger mode = T0 (Continuous on Talk)
# Data format = G1 (without prefixes)
dmm196.write('F0R4P0S3T0G1X')

voltage_array = []
current_array = []
for i in range(0, no_of_measurements + 1):
    voltage_setpoint = max_volts / no_of_measurements * i
    if voltage_setpoint < 3 or i % 20 == 0:
        psu_set_voltage(2, voltage_setpoint)
        # Wait a bit till the circuit settles
        time.sleep(0.3)

        # Measure voltage
        voltage = float(dmm196_read_value(0.2, 0.01))
        print(str(voltage) + " V ", end='')

        # Measure current
        dmm7510.write("FUNC \"CURR\"")
        dmm7510.write(":SENS:CURR:NPLCycles MAX")
        # Convert to mA
        current = float(dmm7510.ask("MEAS?")) * 1000
        print(str(current) + " mA ", end='')
        print(str(current * voltage) + " mW")
        if voltage_setpoint == 24:
            power_at_24VDC = voltage * current / 1000

        # Store the measurements
        voltage_array.append(voltage)
        current_array.append(current)

# Close GPIB connection
rm.close()
psu_off("ALL")

plt.rcParams['figure.dpi'] = 150

fig, ax = plt.subplots()
"$Y_{axis}$"
ax.set(xlabel="$I_{IN}$ (mA)", ylabel="$V_{IN}$ (V)",
       title='Digital input IEC61131-2 Type 1')

y = np.array([[2, 15], [15, 15], [15, 30], [2, 30]])
p = Polygon(y, facecolor='gray', alpha=0.5, edgecolor='black', linewidth=1)
ax.add_patch(p)

y = np.array([[0, 0], [15, 0], [15, 5], [0.5, 5], [0.5, 15], [0, 15]])
p = Polygon(y, facecolor='gray', alpha=0.5, edgecolor='black', linewidth=1)
ax.add_patch(p)

ax.text(8, 22, 'ON', fontsize=15)
ax.text(7, 1.5, 'OFF', fontsize=15)

ax.text(10, 28, 'Power Dissipation', fontsize=12)
ax.text(10, 26, '@$V_{IN}$ = 24VDC $\\rightarrow$ ' + str(round(power_at_24VDC, 2)) + "W", fontsize=10)
ax.text(10, 24, 'Maximum $\\rightarrow$ ' + str(round(voltage_array[-1] * current_array[-1] / 1000, 2)) + "W",
        fontsize=10)
ax.text(10, 22, '$I_{IN (MAX)}$ $\\rightarrow$ ' + str(round(max(current_array), 2)) + "mA", fontsize=10)

ax.set_xlim([-0.1, 15.5])
ax.set_ylim([0, 32])

ax.annotate("", xy=(0, 32), xytext=(0, 0), arrowprops=dict(arrowstyle="->"), alpha=0.6)
ax.annotate("", xy=(15.5, 0), xytext=(0, 0), arrowprops=dict(arrowstyle="->"), alpha=0.6)

plt.xticks(np.arange(0, 15.5, 1))
plt.yticks(np.arange(0, 33, 5))

plt.box(on=None)
ax.plot(current_array, voltage_array, color='r')

plt.show()