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LabView Driver for the AVS-47B and TS-530A
Download the Driver (ZIP)
Download the User Guide (PDF)
This LabView driver covers all the functionality of the AVS-47B Resistance Bridge and the programmable AVS47-IB computer interface. The TS-530A Temperature Controller, which has been discontinued, is also fully supported.
The driver more or less conforms to National Instruments' recommendations ("standards" as they say at NI), consisting of more than 40 VI's. It has been verified with AVS47-IB firmware version 3.4, which comes with new interfaces.
Version 1.2 of the driver was saved in LabView 7.1 format. It can still be loaded into new LabView versions.
The AVS47-IB is not only a program converter or command interpreter: It offers many higher-level functions like averaging, scanning and buffering of results. They can save your computer's resources by reducing the workload of LabView. The driver has also many smaller nice features. Autoranging prevents overloads and averaging of a measured or scanned sensor re-starts after each automatic change of range. The driver can be started, initialized and the control can be set in remote mode without altering the current state of the instruments.
Opening and Closing the Driver
- Initialize
- Establishes the VISA session and configures the AVS47-IB so that it is compatible with the driver. Reset to default state occurs only if allowed and if the unit is not busy.
- Close
- Closes the VISA session. Optionally leaves the AVS-47B in the remote mode so that the state of the bridge cannot be altered by mistake.
High-level VI's
- Discuss
- This VI is the simplest and fastest way to verify connection from LabView to the 47IB. One can send all commands and queries given in the AVS47-IB manual and study their responses as well as the instrument response to various remote commands.
- Getting started
- A simple VI that first reads all "real" front panel settings from the AVS-47B. These settings are taken as initial values which are written back to the bridge once it has first been set in the remote mode. After a selectable delay, one reading is taken. If the VI is run continuously, the soft front panel can be used to change the parameters.
- Application example 1
- A more complex VI demonstrating how VI's for the AVS-47B and TS-530A can be used programmatically to create a new combined instrument. This VI may give some ideas about how to overcome LabView's limitations in handling numbers to implement a legible and understandable display, how to avoid frequent configuring of parameters that have not been changed, and so on.
Configuration VI's
- Configure AVS47
- Configures any or all of: 1) input mode (zero/cal/meas), 2) multiplexer, 3) range, 4) excitation, 5) display.
- Configure AVS47IB
- Configure any or all of: 1) printer enabled, 2) buffer enabled, 3) response message headers included, 4) front panel started measurement enabled, 5) autoranging enabled, 6) stabilisation delay after autoranging.
- Configure addresses
- Configures any or all of: 1) the GPIB device address of the AVS47-IB, 2) the Picobus address of the AVS-47B with which to communicate, 3) the Picobus delay factor.
- Configure TS530A
- Configures any or all of: 1) set point voltage, 2) proportional gain, 3) integration time constant, 4) derivator time constant, 5) bias power, 6) heater power range.
- Enable service requests
- Enables an SRQ (service request) to be asserted by any or both of: 1) message available, 2) operation complete. Our application examples poll the STB instead of using the SRQ.
- Configure time and date
- Takes the current date and time from the computer and programs them into the AVS47-IB. The instrument needs these values for time stamps when saving scan results to buffer. The clock in the inteface is not battery-backed.
- Configure scan
- Configures the SCAN procedure for: 1) first channel to be measured, 2) last
channel to be measured, 3) time interval between scan cycles, 4) enable/disable temperature control between scans, 5) temperature control period between successive channels, if enabled.
- Configure channel
- Configures any selected channel to be SCANned with following settings:
1) stabilisation delay, 2) average count, 3) excitation 4) range (if manual ranging) or initial range (if autoranging).
- Configure reference
- Sets the deviation reference voltage of the AVS-47B (for offsetting the recorder
voltage output) either 1) from the LabView digital control or 2) directly from the measured sensor resistance (null the "recorder" output).
Action/Status VI's
- Go remote
- Sets the AVS-47B in remote mode. The state of the bridge is not altered otherwise.
- Go local
- Sets the AVS-47B in local mode. The state of the bridge is not altered otherwise.
- Poll STB status byte
- Serial polls the STB status byte of the AVS47IB. This is the only VI that can always be used, regardless of whether the interface is busy or not.
- Start one ADC
- Sets the AVS47IB to wait for the completion of the next free-running A/D conversion and store its result. Status is cleared and the OPC bit will be asserted when ready.
- Wait for MAV/OPC/TMO
- Waits for 1) a message becoming available or 2) an operation being completed
or 3) an adjustable timeout being reached.
- Start averaging
- Starts a sequence of n A/D conversions whose average etc. are available. N is the input parameter.
- Start digital filter
- Sets the AVS47-IB in a mode where it measures the selected sensor, in either manual or autorange mode, at full speed, maintaining a running average of the readings. Input parameter is the length of the ring buffer. The current value of the average is asked using a separate VI.
If high-quality readings are needed seldom and the excitation must be low, the digital filter may be an ideal solution, giving the readings quickly once they are needed.
- Stop averaging etc.
- Stops the AVS47-IB if it is averaging or scanning or in any other of the 10 time-taking modes that can be stopped.
- Start single scan
- Starts a single scan cycle using the settings given by "Configure channel parameters.vi". The results are read after the cycle has completed.
- Start continuous scan
- Starts continuous scanning. Input for enabling/disabling buffer storage. If disabled, only results from the last cycle can be read. Scan interval is configured by "configure scan parameters".
Data VI's
- Read single ADC
- Reads the result of the A/D conversion that was started by "Start one ADC.vi". Response is fast, but there is no automatic guarantee that the reading is up to date.
- Read one reading
- This VI is actually in between the Action/status and Data categories. It first initiates an A/D conversion, then waits until the operation completes, asks for the reading and finally reads it. Time required may exceed 400 milliseconds. Waiting time is available to other processes.
- Read average
- Reads the average, started by "Start average.vi". Available are also min, max and standard deviation.
- Read digital filter
- Reads the current value of the running average without stopping the filter. Only the resistance reading is available.
- Read scan channel
- Reads the results of the last completed SCAN measurement of the selected channel. In addition to the resistance reading (average of n conversions), available are also min, max and std.
- Read the buffer
- Reads the results stored in the AVS47-IB buffer. The three modes are
- read only the buffer size and free space
- read the buffer contents and save to a disk file in an easy ASCII format ("spreadsheet")
- as above but finally delete the buffer contents.
- Read AVS47 parameters
- Reads the following settings: 1) input (zero/meas/cal), 2) channel, 3) range,
4) excitation, 5) display 6) position of reference voltage source switch, 7) position of deviation magnifier switch and 8) remote/local mode. This VI is quite slow, because several transactions with the AVS-47B are required.
- Read from TS530A
- There are three parameters that can be measured from the TS-530A: the analog set point voltage, the heater voltage and the heater current. From the last two, the AVS47-IB box calculates the heater power. "Read from TS530A.vi" measures one of the following at a time: 1) set point voltage, 2) heater voltage, 3) heater current or 4) heater power. The VI is quite slow, time needed for function 4 may exceed two seconds.
- Read TS530A parameters
- Reads the TS530A parameters that are currently in the memory of the AVS47-IB: 1) set point, 2) proportional gain, 3) integration time constant, 4) derivation time constant, 5) bias power, 6) heater power range.
- Read AVS47IB
- Reads the following settings: 1) printer enabled, 2) buffer storage enabled, 3)
GPIB address of the box, 4) current Picobus address of the AVS47, 5) Picobus delay factor, 6) message headers included, 7) front panel started measurement enabled.
- Read channel parameters
- Reads the settings that the AVS47-IB is using for a SCAN measurement of
the selected channel: 1) stabilisation delay, 2) average count, 3) excitation, 4) range (if manual ranging) or initial range (if autoranging).
- Read scan parameters
- Reads the settings that the AVS47-IB is using for SCAN measurements: 1) first channel to be measured, 2) last channel to be measured, 3) time interval between scan cycles, 4) temperature control between cycles enabled, 5) temperature control period between successive channels.
Utility VI's
- Reset
- Resets the bridge and the controller to a non-measurement, non-control and non-useful state. Existence of this command is required by the National Instruments' "standards".
- Default setup
- Sets the AVS47-IB ready for LabView operation, enabling OPC and disabling response message headers.
Getting Started.vi explained
This VI initializes a VISA session. Then it reads the positions of the AVS-47B front panel switches. The bridge may be in manual or remote mode. The switch settings are stored in local variables (ran, exc etc...). These variables transfer the values into the corresponding digital controls inside the while loop. Values are read from the variables only once, and hence they can act as initial values, setting the digital controls in correct positions.
The AVS-47B is now set into remote mode, and all the parameters are programmed into the bridge according to the initial values. It takes some time for the bridge to settle, and the time depends on excitation. There is an adjustable delay after the configuration for preventing too early A/D conversions. After the delay, one reading is taken. The resistance value is calculated by the AVS47-IB and output as a real number.
The VI runs until the STOP switch is pressed.
