Measurement Computing PCIM-DAS1602/16 - Manual (Page 13)

PCIM-DAS1602/16 User's Guide Installing the PCIM-DAS1602/16
A/D Range Select switch
The A/D converter range is set by switch S2. This switch controls all A/D channels.
Although you cannot run some channels bipolar and some unipolar, you can measure a unipolar input in the
bipolar mode (for example, you can monitor a 0 to 5V input with a channel set to the ±5 V range). This switch
is factory-configured for bipolar. The A/D Range Select switch shown in
is configured for unipolar. Figure 2-3
Figure 2-3. A/D Range Select switch
Trigger Edge Select jumper
The original Keithley MetraByte DAS-1600 was designed such that A/D conversion initiates on the falling edge
of the convert signal. Neither the original DAS-16, nor any of the other DAS-16 derivative converts on the
falling edge of the signal. In fact, we are not aware of any A/D board that uses the falling edge to initiate the
A/D conversion.
When using the falling edge to start the conversion, the A/D may be falsely triggered by 8254 pacer clock
initialization glitching. False triggering is easy to avoid, but may occur in the DAS-1600. Since initiating
conversions on the falling edge is undesirable, but initiating on the rising edge may lead to timing differences if
the PCIM-DAS1602/16 board is used as a replacement for an older DAS16 series board, the PCIM-
DAS1602/16 is equipped with a jumper that you can use to select the edge that initiates the A/D conversion.
The Trigger Edge Select mode is configured by jumper P8 . This jumper is factory-configured for rising edge.
shows the edge selection options. Figure 2-4
Figure 2-4. Trigger Edge Select jumper
P8
P8
Falling Edge A/D Trigger
DAS-1600 Method
Rising Edge A/D Trigger
DAS-16 Method
Default
Setting
For compatibility with all third party packages, with all DAS-16 software, and with PCIM-DAS1602/16
software, leave this jumper in the default rising edge position.
2-4