QCoDeS Example with QDac

In [1]:
import qcodes as qc
import numpy as np

from time import sleep

from qcodes.instrument_drivers.QDev.QDac import QDac
pyqtgraph plotting not supported, try "from qcodes.plots.pyqtgraph import QtPlot" to see the full error
In [2]:
# Connect to the instrument
qdac = QDac('qdac', 'ASRL6::INSTR', update_currents=False)

Basic QDac Usage

The QCoDeS QDac driver currently supports using

  • 48 Output Channels
  • 3 $\times$ 6 temperature sensors

Each output channel has six parameters:

  • DC voltage
  • DC voltage range
  • Current out (read-only)
  • Current out range
  • slope
  • sync

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).

In [3]:
# Current out is the current flowing through the channel this is read-only
print(qdac.ch01_i.get(), qdac.ch01_i.unit)
3.52608e-06 A
In [4]:
# The current range can be either 0 to 1 μA or 0 to 100 μA
# This is set with either 0 (0 to 1 μA) or 1 (0 to 100 μA) 
100 muA
In [5]:
# The DC voltage may directly be set and gotten
print('Channel 1 voltage: {} {}'.format(qdac.ch01_v.get(), qdac.ch01_v.unit))
Channel 1 voltage: -0.999985 V
In [6]:
# The maximal voltage change (in V/s) may be set for each channel
# An overview may be printed (all other channels have 'Inf' slope)
Channel 1, slope: 1 (V/s)
Channel 2, slope: 2 (V/s)
In [7]:
# now setting channel 1 and 2 voltages will cause slow ramps to happen
In [8]:
# 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
Channel 2, slope: 2 (V/s)
In [14]:
# To each channel one may assign a sync channel:
qdac.ch02_sync(1)  # sync output 1 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.
In [15]:
Cancelled a ramp with a ramptime of 0 s
In [12]:
# syncs are unassigned by assigning 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.

In [ ]:
# Here is a small example showing what to look out for
qdac.ch01_vrange.set(0)  # Attenuation OFF (the default)
qdac.ch01_vrange.set(1)  # Attenuation ON
qdac.ch01_v.get()  # Returns 0.15 V
qdac.ch01_vrange.set(0)  # Attenuation OFF
qdac.ch01_v.get()  # returns 1 V

Overview of channel settings

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.

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Temperature sensors

Physically, the QDac consists of six boards eight 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.

In [ ]:
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)
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