from qcodes.instrument_drivers.QDev import QDevQDac
# Connect to the instrument
qdac = QDevQDac("qdac", "ASRL6::INSTR", update_currents=False)
The QCoDeS QDac driver currently supports using
Each output channel has six parameters:
The slope is the (maximal) slope in V/s that the channel can allow its voltage to change by. By default, all channels have a slope of "Inf". The slope can be changed dynamically, but no more than 8 channels can have a finite slope at any given time (this is due to hardware limitations).
# Current out is the current flowing through the channel this is read-only
print(qdac.ch01.i.get(), qdac.ch01.i.unit)
# The current range can be either 0 to 1 μA or 0 to 100 μA
print(qdac.ch01.irange.get())
# This is set with either 0 (0 to 1 μA) or 1 (0 to 100 μA)
qdac.ch01.irange.set(1)
# The DC voltage may directly be set and gotten
qdac.ch01.v.set(-1)
print(f"Channel 1 voltage: {qdac.ch01.v.get()} {qdac.ch01.v.unit}")
# Multiple channels can be addressed simultaneously via the 'channels' list
qdac.channels[0:20].v.get()
# Similarly, we may set them
qdac.channels[0:2].v.set(-1)
# The maximal voltage change (in V/s) may be set for each channel
qdac.ch01.slope.set(1)
qdac.ch02.slope.set(2)
# An overview may be printed (all other channels have 'Inf' slope)
qdac.printslopes()
# now setting channel 1 and 2 voltages will cause slow ramps to happen
qdac.ch01.v.set(0)
qdac.ch02.v.set(0)
# Note that only 8 (or fewer) channels can have finite slopes at one time
# To make space for other channels, set the slope to inifite
qdac.ch01.slope("Inf")
qdac.printslopes()
# To each channel one may assign a sync channel:
qdac.ch02.sync(2) # sync output 2 will fire a 10 ms 5 V pulse when ch02 ramps
# note that even if no visible ramp is performed (i.e. ramping from 1 V to 1 V), a pulse is still fired.
# The sync pulse settings can be modified
qdac.ch02.sync_delay(0) # The sync pulse delay (s)
qdac.ch02.sync_duration(25e-3) # The sync pulse duration (s). Default is 10 ms.
qdac.ch02.v.set(0)
# syncs are unassigned by assigning sync 0
qdac.ch02.sync(0)
The v_range parameter is really controlling a 20 dB (amplitude factor 10) attenuator. Upon changing the vrange, the attenuator is immediately applied (or revoked). This will --irrespective of any slope set-- cause an instantaneous voltage change unless the channel voltage is zero. By default, all attenuators are off, and the voltage range is from -10 V to 10 V for all channels.
# Here is a small example showing what to look out for
#
qdac.ch01.vrange.set(0) # Attenuation OFF (the default)
qdac.ch01.v.set(1.5)
qdac.ch01.vrange.set(1) # Attenuation ON
print(qdac.ch01.v.get()) # Returns 0.15 V
qdac.ch01.v.set(0.1)
qdac.ch01.vrange.set(0) # Attenuation OFF
print(qdac.ch01.v.get()) # returns 1 V
The driver provides a method for pretty-printing the state of all channels. On startup, all channels are queried for voltage and current across them, but the current query is very slow (blame the hardware).
The pretty-print method may or may not update the values for the currents, depending on the value of the update_currents flag. Each current reading takes some 200 ms, so updating all current values takes about 10 s.
qdac.print_overview(update_currents=True)
Physically, the QDac consists of six boards each hosting eight channels. On three locations on each board, a temperature sensors is placed. These provide read-only parameters, named tempX_Y where X is the board number and Y the sensor number.
print(qdac.temp0_0.get(), qdac.temp0_0.unit)
print(qdac.temp2_1.get(), qdac.temp0_0.unit)
print(qdac.temp5_2.get(), qdac.temp0_0.unit)
qdac.close()