Bipolar Operation

Bipolar Firmware

To verify that you are running the correct firmware, you can run the following command in the ARDI console:

psu.ask('hardware')

Which should return something like:

'PS2-08-A (BIPOLAR)'
# or
'A1x8 (BIPOLAR)'

Connecting Actuators

When operating in bipolar mode, the loads must ALWAYS be connected to an adjacent pair of output channels (7), and NEVER to a common ground connection. In other words, an individual actuator should be connected to channels 1&2, 3&4, 5&6, or 7&8. In this configuration, the actuator can be controlled as ch12, ch34, ch56, or ch78, respectively.

Automatic Calibration

Upon switching HV on, the power supply calibrates to the connected load and and selects control parameters accordingly. Incorrect control parameters may damage actuators or the power supply itself.

To change connected loads, always turn off HV, disconnect the load, and then turn HV back on. The power supply will re-calibrate to the new load and select appropriate control parameters for driving it.

Please note that during calibration, all channels will output up to 1kV.

Bipolar Waveforms

zero

chXY.zero()

Zero the output of the channel.

voltage

chXY.voltage(amp)

Output a constant amp volts on channel chXY. This value can be positive or negative.

Example:

import ardi
psu = ardi.autoconnect()
ch12 = psu.channels['ch12'] # bipolar
ch12.voltage(5000) # set ch12 to 5kV
ch12.voltage(-5000) # set ch12 to -5kV

waveform

chXY.waveform(xs, dt=1000)

Output a waveform defined by xs on channel chXY. The waveform is defined as an iterable list of integer voltage values in V, and is played at a rate of dt microseconds per point. All waveforms are played repeatedly in a loop. Bipolar waveforms can take values from -v_rail to +v_rail.

Please note that at the moment, only 5000 points can be stored in the waveform memory. If the waveform is longer than 5000 points, it will be truncated. This number is expected to increase with future firmware updates.

Example:

import ardi
import numpy as np
from numpy import pi
# goal: superimpose two 2.5kV sinusoids with different frequencies
# to make a more complex 5kV waveform (-2.5kV to 2.5kV)
dt = 1000 # sample rate, 1000 microseconds/sample is a good default
f1 = 1 # Hz
f2 = 5 # Hz
# create a time vector (in seconds) long enough to hold a full period
ts = np.arange(0, 1, (f2*dt)/1e6)
# sample the waveform
xs = [2500*(np.sin(2*pi*t*f1) + np.sin(2*pi*t*f2) ) for t in ts]
# connect to and program the device
psu = ardi.autoconnect()
ch12 = psu.channels['ch12'] # bipolar
ch12.waveform(xs, dt)

sin

chXY.sin(freq, amp, phase=0)

Output a sinusoid with a frequency of freq Hz and an amplitude of amp V on channel chXY. Phase is optional, defaults to zero, and takes values in degrees. Bipolar channels output positive or negative voltages. For example, a bipolar sinusoid with an amplitude of 1000V will oscillate between +/- 500V.

Example:

import ardi
psu = ardi.autoconnect()
ch12 = psu.channels['ch12'] # bipolar
ch12.sin(1, 5000) # 1 Hz, -2.5kV to 2.5kV

square

chXY.square(freq, amp, duty=0.5)

Output a square wave with frequency freq Hz, amplitude amp V, and duty cycle duty on channel chXY. The optional duty cycle argument defaults to 0.5, and takes values between 0 and 1. 0 corresponds to a 0% duty cycle, and 1 corresponds to a 100% duty cycle. Although bipolar channels can output negative voltages, this function only generates unipolar voltage patterns. In other words, the square wave will oscillate between 0 and amp V. Please note that amp may be positive or negative.

square (alternating polarity)

chXY.square_alt(freq, amp, duty=0.5)

Output a square wave with alternating polarity on each high state. In other words, the square wave will step through the pattern [0, amp, 0, -amp] V. Otherwise, this function behaves identically to chXY.square.

chirp

chXY.chirp(f0, f1, T, amp, bounce=True)

Output a chirp signal, or in other words, a sinusoid with a variable frequency sweeping between f0 and f1 Hz over a period of T seconds. The amplitude of the chirp is amp V. Bipolar channels output positive or negative voltages. For example, a bipolar chirp with an amplitude of 1000V will oscillate between +/- 500V.

Bounce is an optional argument that defaults to True. When bounce is True, the chirp will sweep back and forth between f0 and f1 Hz. When bounce is False, the chirp will sweep from f0 to f1 Hz and then immediately jump back to f0 Hz.