Digital Multimeter Examples

Initial Setup

Import the digital multimeter class from inspy.instrument.digitalmultimeter. The device connection can be managed by using the connect() and disconnect() methods. However, the use of context managers (see trace example) is recommended.

import matplotlib.pyplot as plt

from inspy.instrument.digitalmultimeter import DmmKeysight34465A

ADDRESS = "USB0::10893::257::MY57500323::0::INSTR"
dmm: DmmKeysight34465A = DmmKeysight34465A(ADDRESS)
dmm.connect()
dmm_id = dmm.get_id()
print(dmm_id)

Keysight Technologies,34465A,MY57500323,A.02.14-02.40-02.14-00.49-03-01

Simple Measurements

Single measurements can be made using the measure methods.

voltage = dmm.measure_voltage()
current = dmm.measure_current()
voltage_ac = dmm.measure_voltage_ac()
current_ac = dmm.measure_current_ac()
resistance = dmm.measure_resistance()
resistance_four_wire = dmm.measure_resistance_four_wire()
continuity = dmm.measure_continuity()
frequency = dmm.measure_frequency()
period = dmm.measure_period()

print(f"Voltage: {voltage} V")
print(f"Current: {current} A")
print(f"AC Voltage: {voltage_ac} V")
print(f"AC Current: {current_ac} A")
print(f"Resistance: {resistance} Ohms")
print(f"4-Wire Resistance: {resistance_four_wire} Ohms")
print(f"Continuity: {continuity}")
print(f"Frequency: {frequency}")
print(f"Period: {period}")
dmm.disconnect()

Voltage: 1.17625601e-05 V
Current: 3.16225072e-12 A
AC Voltage: 0.00119330846 V
AC Current: 0.0 A
Resistance: 9.9e+37 Ohms
4-Wire Resistance: 789.106695 Ohms
Continuity: True
Frequency: 99.9656529
Period: 0.0100052345

Trace Example

Trace functions include: 'VOLT', 'VOLT:AC', 'CURR', 'CURR:AC','RES', 'FRES', 'TEMP', 'FREQ', 'PER', 'DIOD', 'CONT', 'CAP'. Note averaging time can only be set for 'VOLT', 'CURR', 'RES', 'FRES', 'TEMP'.

with DmmKeysight34465A(ADDRESS) as dmm:
    # Set the trace function you want to measure
    dmm.set_sampling_measurement_mode(function="VOLT")

    # Optional: Configure averaging time and measurement range and trigger delay.
    # See measurement section below.
    dmm.set_measurement_range(measurement_range=1)
    dmm.set_averaging_time(averaging_time=0.01)

    # Configure sampling
    dmm.set_sample_points(sample_points=100)
    dmm.set_measurement_range(measurement_range=1)
    dmm.set_sample_interval(
        sample_interval=0.03
    )  # Must be at least 2.1x bigger than averaging time?

    # Configure trigger
    dmm.set_trigger_immediate()
    dmm.set_trigger_delay(trigger_delay=0.01)
    dmm.set_wait_for_trigger()  # Set state to wait-for-trigger

    # Read samples
    samples = dmm.get_samples(
        polling_cycle=1
    )  # Blocks code, waits for trigger event and measurements to complete.
    # Sets polling cycle to 1 second.
    print(f"Sampled Values:{samples}")

    # Reset Instrument to factory default.
    dmm.reset()

Sampled Values:[-0.000174865096, 0.000189855769, -0.000160194402, 0.000166605493, -0.000140659566, 0.000146773698, -0.000122314868, 0.000126154617, -9.79458165e-05, 0.000105457267, -7.23774188e-05, 8.40969392e-05, -5.56556361e-05, 6.23982162e-05, -2.82502364e-05, 4.05728828e-05, -9.15508396e-06, 1.91112665e-05, 5.81026701e-06, -4.8273098e-06, 2.87520741e-05, -2.25205397e-05, 4.86828553e-05, -5.37564799e-05, 6.85837104e-05, -6.82361073e-05, 9.37124246e-05, -9.03100575e-05, 0.000118610938, -0.000119216366, 0.000143131922, -0.000129066656, 0.00016075379, -0.000154674188, 0.000179429977, -0.000172809403, 0.000196957462, -0.000199558731, 0.000220764824, -0.000220559946, 0.000240382533, -0.000235513787, 0.00025604309, -0.000261367633, 0.000277799363, -0.000278130852, 0.000299311623, -0.000301735637, 0.000322071572, -0.000318112119, 0.000339944358, -0.000338959099, 0.000362170241, -0.000360940969, 0.000383054053, -0.000381058213, 0.000402139998, -0.000396196214, 0.000426852049, -0.000419453396, 0.000447397466, -0.00043510935, 0.000468997203, -0.000462332891, 0.000480302362, -0.000483014126, 0.000503002458, -0.00050177779, 0.000522000926, -0.000518973786, 0.000550329431, -0.000538020596, 0.000565672311, -0.000555202781, 0.000587522967, -0.000582819965, 0.000607508996, -0.000601829943, 0.00062633021, -0.000620791579, 0.000640192899, -0.000643516997, 0.000669023241, -0.000659511346, 0.000683482151, -0.000684909395, 0.000706555172, -0.000703974621, 0.000725671043, -0.000723813322, 0.000745178255, -0.000735284226, 0.00076344008, -0.000754895028, 0.000783221231, -0.000774567984, 0.000805444812, -0.000799187955, 0.000820251324, -0.000816770688]

# Plot Function
plt.plot(samples)
plt.title("Voltage Trace")
plt.xlabel("Time(s)")
plt.ylabel("Voltage(V)")
plt.show()

Trigger sources explained

dmm.connect()

Immediate

Triggers immediately after the instrument is put into wait-for-trigger state.

dmm.set_trigger_immediate()
dmm.set_wait_for_trigger()  # Triggers straight away.

External

Triggers when a TTL pulse is received on the Ext-Trig input.

dmm.set_trigger_external(pos_edge=False)  # Negative slope triggering
dmm.set_wait_for_trigger()

Bus

Triggers when a *TRG command is received.

dmm.set_trigger_bus()
dmm.set_wait_for_trigger()
dmm.trigger_now()

Level

Triggers on a level on the input signal.

dmm.set_trigger_internal_level(trigger_level=3, pos_edge=True)
dmm.set_wait_for_trigger()

dmm.disconnect()

Measurement time explained

The first sample starts one trigger-delay time after the trigger. However, the second sample starts one sample interval after the start of the first sample, and so on:

from IPython.display import Image

Image("images/sampling.png")

The minimum sample time is measurement dependent. It depends on such things as the integration time (set_averaging_time()), autozero on or off, autorange on or off, and the measurement range. Basically, MIN is automatically determined so that the sample interval is always greater than the sampling time (see above illustration). Use dmm.get_sample_interval_min()/dmm.set_sample_interval_min() to determine the recommended interval for the current measurement configuration.