Hawk GUI: Component Cal

Component calibration is based on a calibration database, where the user will define all the measurement devices used:

  • Acquisition cards
  • Signal conditioners
  • Pre-amplifiers
  • Wires
  • Sensors

Those devices will be calibrated (amplitude and frequency domain calibrations) at regular interval. To calibrate a device, the user has the choice between:

  • AC calibration
  • Manual calibration
  • SPL calibration for microphones

When using component calibration as first calibration method on a channel, the user will specify the devices within the measurement chain. The calibration of each device will be combined to compute the overall amplitude and frequency response of the channel. So there is no need to perform a live calibration on each channel before every test, as long as the devices used are still within cal.

Calibration Database

Manage devices

Upon clicking on the “Update devices” button (see above), any acquisition cards or signal conditioners (embedded on the acquisition card or standalone) currently in the test cell will be added to the database. In the example below, we have a single dragonfly with embedded 14-02 conditioning.

  1. Select the category of devices, in our example Acquisition card. Other categories are conditioners, pre-amplifiers, wires and sensors.
  2. List of the acquisition cards presents in the system, auto-populated when the user clicked on the “Update devices” button. Select a device to view its details and calibration.
  3. General details of the selected device. For wires, this will include the wire length. For sensors, this will include the sensor nominal sensitivity (mv/EU and EU offset).
  4. Edit general details of selected device
  5. Remove selected device from the database
  6. Add a new device of the selected category (from step 1) to the database. Add button is greyed out for acquisition card, those can only be auto-populated.
  7. List of the gain available on the device. On applicable to conditioners and pre-amplifiers, where we maintain calibration data for each gain. For the other types of devices, there is no gain so there is a single gain entry of 1.
  8. Tick the appropriate check box to display the time domain calibration or frequency domain calibration.
  9. Graph showing time domain or frequency domain calibration. In our example, the time domain calibration of the acquisition card shows ADC count measured vs voltage on the card input. Note that the default calibration when the device is automatically added will be flat frequency response, and linear 1 mV in 1 mV out amplitude response.
  10. To manually edit the calibration data, will take the user to a screen identical to the manual calibration screen.
  11. To perform a live calibration on the device.

  1. User has selected conditioner device type
  2. List of the conditioners in the test cell.
  3. For the conditioners, we maintain the calibration data for each gain. Select a gain to see the corresponding calibration data.
  4. “Cal interval days” defines how often the device should be re-calibrated. Each time the device is calibrated, that offset is applied to the calibration date, to compute the end calibration date.
  5. End calibration date can be overwritten by the user if he wishes to continue using a device that is past its calibration end date, without re-calibrating it. The date is displayed in red when we are past it. In our example, the device has never been calibrated…
  6. When changing the calibration end date, tick this check box to apply the new date to all gains. Tick the box before editing the date.
  7. A single amplitude response is maintained for a gain of 1. For every other calibrated gain, a gain multiplier is computed on the back of the live calibration. For example, for a gain of 2, the gain multiplier might come out as 1.99. In this case, during scanning, if the user selects a gain of 2 for this channel, the actual gain that will be taken into account when converting the ADC into EUs will be 1.99, instead of 2.
  8. The graph is empty as the device has not been calibrated yet.

Calibrate a device

  1. Select a device and drop it onto a calibration chain in 2. Note that if the device selected is an acquisition card with embedded conditioning, the corresponding conditioner device will be dragged along with the acquisition card, and vice versa.
  2. The calibration chains.
    Each row is a measurement chain. The chain should always end with the acquisition card (signal path goes from left to right). The device to calibrate or recalibrate is the one at the beginning of the chain (first device in the signal path, or “entry” device).
    Devices displayed with a green colour are already calibrated; devices in red are yet to be calibrated. There cannot be more than one device to calibrate in each chain, and it should be the first device in the chain (so on the left). Otherwise, the chain is considered to be invalid, and the calibrate device button will be disabled.
    During the calibration, the response of the whole chain is measured. Starting from the output of the acquisition card (the ADC counts) and working backwards using the devices’ current calibration, we can work out what the amplitude of the signal coming out of the entry device was. The signal coming into the entry device is known, it is given by the user in 8. We are therefore able to compute the response of the entry device.
    It is possible to calibrate multiple devices at the same time, by assigning each of them to a different measurement chain.
    A device can only be present in one chain, except for wires. For those, the user will define a device for each type and length of wire, so there can be multiple instances of the same wire “device” in a given measurement chain, or across multiple chains.
    For conditioner devices, user will select which gain to apply during calibration. If the conditioner is the device being calibrated (this is the case in our example), the calibration data computed will be stored against this gain in the database.
  3. Remove a device from a chain by dragging it and dropping it onto the recycle bin.
  4. Scroll vertically through the calibration chains, as there might be more chains than we can display in the screen.
  5. Scroll horizontally through the devices in the chain, as there might be more devices in a chain than we can display.
  6. Click on the red cross to come back to the main screen
  7. Choose the live calibration method to use (AC response or SPL for microphones) and the acquisition bandwidth.
  8. In our example, AC calibration has been chosen, so the user has to put in the amplitude of the signal that will be injected in the measurement chain. Amplitude specified will be in millivolts if the device being calibrated (the “entry” device) is not a sensor, in EUs if we are calibrating a sensor.
  9. Start the live calibration, in our example AC response. This will take the user to the regular calibration screen
  10. Perform a calibration check: the user will go through a similar process to the live calibration. At the end of the calibration check, the user will be prompted to save the calibration report on disk, on a location of his/her choice. The report is a CSV file, showing for each measurement chain
    1.       The devices in the chain
    2.       The measured amplitude (based on the current calibration data)
    3.       The expected amplitude
      The calibration check has no effect on the calibration data stored in the Database.

Component Cal Method

Use will select “COMPONENT” method as the first calibration method for a given channel:

Then he/she will define the measurement chain for this channel, in the component cal tab of the Channel Configuration screen. The tab may need to be activated first in the preferences:

As shown above, the user will define how many devices are in the chain. For each device, he/she will select its type and name (drop down list populated from the devices defined in the calibration database). Note that the chain is always terminated by an amplifier and acquisition card, that will be worked out at run-time (i.e. when configuring the system), based on the device that is mapped to the channel at the time.

When configuring, for each chain, the calibration data of each device is combined to compute the channel overall calibration. If a device in use is past its end calibration date, the user will be prompted when configuring; he/she may choose to continue the configuration, or abort.

Correction factor

For chains that begin with a sensor (as in example above), the user may choose “CORR. FACTOR” as secondary calibration method. This is optional, and is used to correct the sensor sensitivity on the day of the test, depending on the test conditions (temperature, etc.).

Chain without a sensor

If the chain defined does not begin with a sensor, the user will define mv/EU as the second calibration method: