Digital control of external devices
This window lets you set up computer-controlled switching of up to eight external devices through the digital outputs of a UI2, UI3, or Datataker.  If you are using an ADC-1, the maximum number of switched devices is six.  At present, this function is not implemented for the Advantech ADAM series.

NOTE:  external device control is not available for the Oscilloscope or Multichannel Oscilloscope modes.

CAUTION:  external devices, unless they run at ~ 5 volts with extremely small current drains (e.g., LED's), cannot be driven directly.  Instead, switch devices through relays, preferably via opto-isolators.  The computer's device control lines require devices to be connected to both power and ground.  The voltage goes high when a device is switched 'on'.

Warning:  If you connect ANY external device to a computer, the responsibility for safe operation is yours, and yours alone.  There are NO guarantees or warranties associated with Warthog Systems, and I and the University of California accept no liability of any kind for the use of this software.

  •   LabHelper works well with Sable Systems respirometry multiplexers (these are 4- or 8-channel computer-controlled valve banks), but there are a few special considerations.

  •   With some A-D converters (DataTakers, ADAM modules), you may need to build a simple circuit in order to provide the correct control voltage to external devices.

  •   LabHelper's switching modes alternate between sample and reference readings on single or multiple channels.  In essence, the computer selects which single device in a group is connected to a sensor at a given time -- either the reference device is connected or one of several possible sample devices.  This is particularly useful for making measurements of metabolism or evaporative water loss during flow-through respirometry.  Five switching modes are selected from the pop-up menu.  In all modes, no more than one of the eight possible devices is switched on at a given time unless you select the '2 Device Groups' option and your AD converter and the unit it is controlling can handle simultaneous operation of two devices. In the latter case, devices 1 through 4 are the first group and devices 5 through 8 are the second group, and TWO sample devices are switched on simultaneously (one from each group).
            There is one reference device in the normal mode (selected from either group).  If you have selected two device groups, you must select one reference device from EACH group.  To use this option properly, you must have appropriate plumbing AND make sure that at least one sample device is selected from BOTH Group 1 (devices 1-4) and Group 2 (devices 5-8).  Note: the '2 Device Groups' option is not available with the Sable UI2 or UI3, due to the way their output signals are coded.

    In this example, the computer is controlling a cluster of 8 solenoid valves.  Four of these (2, 4, 6, and 8) are connected to different animal chambers.  The '2 Device Groups' option is used to split the 4 sample streams into two groups, each of which is sampled -- ONE AT A TIME -- by one channel of a 2-channel gas analyzer.  Note that for each 'bank' of valves, another input besides the two connected to animal chambers must contain a stream of reference air (for example, devices 1 and 5).  Also, the best arrangement for most analyzers is to 'sip' a small fraction of the excurrent air stream from each chamber.  The 'sippers' and gas scrubbers are not shown here for clarity.

    • Note:  the two groups are 1-3 and 4-6 when using the ADC-1.

    Top of page

  •   Depending on hardware, LabHelper has two ways of coding the digital signals to the external device, selectable with the output code buttons in the upper right:

    one line per device.  Each of the output lines in the I/O port is connected to a single device.  When the line goes high, the device it is connected to is switched on.

    three-bit word.  The external device must decode a signal sent on three digital I/O lines (each line represents one bit of the three-bit signal, yielding 8 possible values).  NOTE: this coding mode does not allow the '2 Device Groups' option. The Sable Systems multiplexer uses this control scheme (see the special considerations page).

  •   The general switching pattern is shown in a simple graphic display at the right of the window.  Thick bars symbolize a channel being sampled; thin bars represent reference periods; thin lines indicate times when a channel is switched off (i.e., set to zero) while another channel in the same device group is being read.   In this example, two devices (#1, #2) are in use for sampling data.  Device 4 is used for reference.

    The Switch Markers and Zeroing Options button gives you some control over how switching information is stored in the data file.  For markers, you can use either R for reference and S for sample, or the number of the device being switched.   So in the example above, the latter option would place the marker 4 in the file whenever the systems switched to reference and either 1 or 2 when it switched to sampling.

    When there are more than one sampling devices, the default is to enter zero, or some other user-set value, when a sampling device is not in use.   So in the example above, when device 1 was being sampled, a constant -- zero or some other number -- is placed into the channel associated with device 2.

    The window in which you select these options looks like this (here the user has selected 18 as the 'zero' value for periods when a sampling device is not in use):

    Top of page


  • The switching modes are:

  •    OFF     (no device switching).

  •   MANUAL (KEYBOARD) DEVICE SWITCHING     The computer turns on a reference device at the start of a data collection run.  The reference device is switched off and a sampling device is switched on when the '+' (plus-sign) key is struck.  The reverse occurs when the '-' (minus-sign or dash) key is struck.  [Two reference or sampling devices are switched on simultaneously if the 2 Device Group option has been selected.]

    If this mode is selected, the user must designate (1) a reference device from the panel in the middle left of the screen, and (2) a sampling device from the panel located at the bottom of the screen.  Sampling devices are assigned to particular data channel(s) by entering the appropriate device number for the correct channel in the blue edit fields at the bottom left of the screen (select device number 0 to leave a channel unassigned).  The 'Setup OK' button will be deselected until all these conditions are met.  Click the 'Check Configuration' button to insure that LabHelper recognizes any changes.

  •    KEYBOARD SWITCHING (WITH TIMER)     This is similar to manual keyboard control, except that the computer automatically switches back to sampling after a specified reference interval has elapsed.  Accordingly, you must specify a reference interval in addition to the reference device and sampling device.

  •   SWITCH TO REFERENCE AT START AND FINISH OF RUN     The computer turns on a reference device for a designated period (the reference interval) at the start of a data collection run, then switches to a sampling device for most of the rest of the run.  At the end of the run, the sampling device is switched off and the reference device is switched on for a time equal to the reference interval.  [Two sampling devices are switched on simultaneously if the 2 Device Group option has been selected.]

    If this mode is selected, the user must designate (1) a reference device from the panel in the middle left of the screen, (2) a sampling device from the panel at the bottom of the screen, and (3) a reference interval > zero, entered in the edit field in the upper right of the screen.  Note that only the FIRST sampling device selected will be switched, so select 1 only.  Sampling devices are assigned to particular data channel(s) by entering the appropriate device number for the correct channel in the blue edit fields at the bottom left of the screen (select device number 0 to leave a channel unassigned).  The 'Setup OK' button will be deselected until all these conditions are met.  Click the 'Check Configuration' button to insure that LabHelper recognizes any changes.

    Top of page

  •    PERIODIC REFERENCE, ONE OR MORE CHANNELS     LabHelper switches on the reference device(s) for a reference interval at the beginning of a run, then steps sequentially through a series of sample devices.  The first sample device in the sequence is switched on for a time equal to the sequence interval.  At the end of this interval, the reference devices are switched on for a time equal to the reference interval.  Then the next sample device is turned on for a duration equal to the sequence interval, and the process continues.  When the last sample device has been selected and switched, the cycle is repeated.  This scenario continues until the data collection run is complete.

    The 'paradigm' for this mode is switching several different air streams through a single set of gas analyzers.  Note that whenever a sample device is switched on, among the data channels which have sample devices assigned to them only the channel(s) assigned to the currently selected sample device(s) will record data.  The other channels with assigned sample devices will register zero volts.  Thus an assigned channel only records data when its assigned sample device is selected and operating.  All non-assigned channels record data at all times, and all channels (including channels with assigned sample devices) record data during reference intervals.  [2 reference and 2 sample devices are switched on simultaneously if the 2-group option has been selected.]

    If this mode is selected, the user must designate (1) reference device(s) from the panel in the middle left of the screen, (2) one to seven sampling devices from the panel at the bottom of the screen, (3) a reference interval >0, and (4) a sequence interval > 0, which must be entered in the edit field in the upper right of the screen.  Sampling devices are assigned to particular data channel(s) by entering the appropriate device number for the correct channel in the blue edit fields at the bottom left of the screen (select device number 0 to leave a channel unassigned).  The 'Setup OK' button will be dimmed (deselected) until all these conditions are met.  Click the 'Check Configuration' button to make sure that LabHelper recognizes any changes.

    Top of page

  •   START & END, SEQUENTIAL FILES     This mode resembles the periodic references mode, except that each external device is associated with a separate file instead of a separate channel.  A single channel (in the example below, channel 1) is switched among several external devices.  The computer records one file from the first sample device (with references at the beginning and end), then records another file from the second sample device, and so forth until all assigned sample devices have been used and the cycle repeats.  In the example below, device 1 is the reference device, and the sample devices are 2, 3, 5, and 7.  When this mode is selected, the autorepeat option is switched on by default.

    If this mode is selected, the user must designate (1) a reference device from the panel in the middle left of the screen, (2) at least one sampling device from the panel at the bottom of the screen, and (3) a reference interval > zero, entered in the edit field in the upper right of the screen.  The 'Setup OK' button will be deselected until all these conditions are met.  Click the 'Check Configuration' button to insure that LabHelper recognizes any changes.

    The bottom section of the device control window looks like this when switched to sequential files mode.  There is a select button for each logical channel, and a numbered button for each possible external device (6 for the ADC-1; 8 otherwise):

    In this example, there are eight logical channels and channel 3 is sequentially switched between 2 different external devices.  Devices 1 and 4 are recorded from on sequential files (another device is used for reference).   The 'no references between channels' button is not selected, which means that a reference is taken at the start and end of each file.   If this option was selected, one of the devices would have to serve as a reference (if a reference was needed).

    • Note that when changing from this mode to other modes (and vice versa), all device assignments are lost. 

    Top of page

    In order to facilitate correct identification of a recorded file with an assigned device, the computer will add a prefix to the "comments" string saved with Warthog format files.  The default prefix is "device 1", "device 2", etc, but you can assign any identifier you wish (with a maximum length of 20 letters).  This window -- opened automatically whenever you access the External Devices window in Sequential Files mode -- allows customization of the identifier strings.  You can also access this window from the Options window.  Example at right:

    During data acquisition in either Switch to Reference at Start and Finish of Run mode or Periodic Reference mode, the operator can manually switch between the reference device and the current sample device by hitting the '-' or '+' keys, respectively.

  • EXTRA ZERO LINKAGES...     Zero linking is an option for periodic references, when one external device switches two logical channels.   In this situation it is useful for the second channel to record zero when not 'connected' to the switched instrument.   Zeroing helps to avoid confusion during analysis -- it's less likely that an incorrect assignment of data to animal will occur (the 'primary' channel automatically records zero when not 'connected').

           

    To 'link' another channel to a primary channel, click the appropriate button to the right of the primary channel's label; when everything is appropriate, click the 'OK' button.


    go to: