DAS20 BOARD MENU CONTROLS:

• Channel
• Range
• External Trigger
• DDisk Remote
• Averager Remote
• Pulse Output
• Pacer Source

CHANNEL CONTROL:

RANGE CONTROL:

    +/- 10 V
    +/- 5.0 V
    +/- 0.5 V
    +/- 50mV

EXTERNAL TRIGGER INPUT BIT:

NOTE:
Daqarta always uses the word "trigger" to mean "start collecting a sweep of N samples". Board manufacturers sometimes use "trigger" to mean "start one ADC sample conversion", but the same manufacturer may alternate between these two meanings in different contexts. Be very wary of references to "external trigger" inputs in a manufacturer's literature: They usually mean "external pacer".

DDISK REMOTE CONTROL INPUT BIT:

AVERAGER REMOTE CONTROL INPUT BIT:

TRIGGER PULSE OUTPUT BIT:

PACER SOURCE:

Few users will have need for the External Pacer mode, or have the special equipment needed to support it, but it offers very powerful benefits for certain applications. This mode allows the sample rate to be controlled externally, to provide exact synchronization to some external process. The external pacer signal may be fixed, or dynamically variable. For example, if you provide a sample clock that is synchronized to an engine or other machine's operating speed, you can view vibration spectra where each harmonic stays at the same screen location even as operating speed varies.

You must provide an external TTL clock signal at exactly the desired sample rate. Connect it to the "External Pacer" input (pin 26). (The DAS-20 documentation refers to this pin as "Cntr #1 Src / Ext Trig", but their usage of "trigger" varies... they really mean "pacer" here.)

Daqarta will make no attempt to determine the actual sample rate... X-axis markings and readouts will still be controlled by the normal X-axis menu, but they will have no effect upon the true sample rate. That's completely controlled by the TTL pacer signal you feed to the pin 26 input. You must insure that this never goes faster than the maximum sample rate (about 100 kHz), or you will get trashy data. (It will probably look like a version of the true waveform, with a forest of spikes growing out of it.)

However, the sample rate menu setting does affect certain other internal functions that deal with time units. When a Trigger Delay is set, the entered time value is converted internally to an equivalent number of sample periods. The delay operation is then carried out by counting samples. So if the true sample period is different from the setting, all trigger delays will be off by the same proportion. Dynamically changing the external sample clock will produce changing delays.

In RTime mode, Cycle times are handled just like Trigger Delay and will show the same sample clock effects. Sequential mode Cycle timing will be correct, since it is done with the system timer using absolute time, not sample counting. The Cycle adjustment control uses the same sample-period increment size in both RTime and Sequential modes, and is limited to a total of 32767 samples maximum, so the sample rate setting will affect both resolution and range.

If you use a varying External Pacer clock frequency during stimulus generation with the STIM3 Stimulus Generator or the Trigger Pulse option, the output frequencies will be scaled accordingly. The sample period established by the X-axis menu items will be used as the basis for STIM3 timing calculations, both for DAC sine waves and DigOut digital output pulses. All durations (Start, Rise, etc) are given in sample periods that may thus be variable in width.

CONNECTOR PINOUT DIAGRAM:

                DAS-20
              .--------.
         Ch0  | 1    2 |  Ch8, Ch0 Lo
         Ch1  | 3    4 |  Ch9, Ch1 Lo
         Ch2  | 5    6 |  Ch10, Ch2 Lo
         Ch3  | 7    8 |  Ch11, Ch3 Lo
         Ch4  | 9   10 |  Ch12, Ch4 Lo
         Ch5  | 11  12 |  Ch13, Ch5 Lo
         Ch6  | 13  14 |  Ch14, Ch6 Lo
         Ch7  | 15  16 |  Ch15, Ch7 Lo
  Analog Gnd  | 17  18 |  Analog Gnd
  DAC 0 Out   | 19  20 |  DAC 1 Out
  Analog Gnd  | 21  22 |  Analog Gnd
 Digital Gnd  | 23  24 |  Digital Gnd
 Sample/Hold  | 25  26 |  External Pacer
 Cntr 1 Gate  | 27  28 |  Cntr 1 Out
  Cntr 2 Src  | 29  30 |  Cntr 2 Gate / Ext Int
  Cntr 2 Out  | 31  32 |  +5 Volts
 Digital Gnd  | 33  34 |  Digital Gnd
   Dig Out 0  | 35  36 |  Dig Out 1
   Dig Out 2  | 37  38 |  Dig Out 3
   Dig Out 4  | 39  40 |  Dig Out 5
   Dig Out 6  | 41  42 |  Dig Out 7
    Dig In 0  | 43  44 |  Dig In 1
    Dig In 2  | 45  46 |  Dig In 3
    Dig In 4  | 47  48 |  Dig In 5
    Dig In 6  | 49  50 |  Dig In 7
              `--------'

DAS20.ADC Revision History:

 8-1-01     Bug Fix:  When generating long stimulus bursts in
            RTime mode, hitting Pause caused sample overrun
            error.


 3-1-01     Added support for STIM3A Dynamic Mode, update for
            Daqarta v2.00.


 11-24-98   Bug Fix:  If F:0 parameter was used to prevent Help
            File loading, then hitting ENTER from the ALT-H
            Help summary screen gave a blank screen instead of
            the proper 'Help file missing!" message.


 8-18-98    Initial release.

DAS20 INDEX:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A:

 Address Parameter A: 
 AUTOEXEC.BAT ignored 
 Averager Remote Control Bit 
 Averager Remote Parameter Preset 

B:

 Board Menu Controls 

C:

 Channel Control 
 Channel Preset Parameter C: 
 Configuration Parameters 
 Connector Pinout Diagram 

D:

 DAC Output Range 
 Digital I/O Preset 
 DDisk Remote Control Bit 
 DDisk Remote Parameter Preset
 DMA Level (D: Parameter)

E:

 External Pacer 
 External Trigger Control 
 External Trigger Parameter Preset

F:

 F: Parameter (Help File Omit) 
 Features, DAS-20 

G:

 Gain (Range) Control 
 Gain (Range) Preset Parameter R: 

H:

 Help File Parameter F: 

I:

 Input Range Control 
 Input Range Preset Parameter R: 
 Introduction - DAS-20 Features 
 IRQ (Interrupt Request) Parameter I: 

O:

 Output Range, DAC 
 Oversampling with STIM3 

P:

 Pacer, External 
 Parameters, Configuration 
 Parameter Overview 
 Pinout, DAS-20 Connector 
 Port I/O Preset Parameter P:
 Pulse Output Bit 

R:

 Range Control 
 Range Preset Parameter R: 
 Remote Control Bit, Averager 
 Remote Control Bit, DDisk 
 Revision History 

S:

 STIM3 DigOut vs Pulse Outputs 
 STIM3 Oversampling Factor 

T:

 Trigger Pulse Output Bit 
 Trigger, External 
 Trigger, External Parameter Preset 
 Trigger, Sweep vs Conversion Terminology 

W:

 Wiring Diagram, DAS-20 Connector

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