Measurement Computing Personal Daq rev.6.0 - Manual (Page 22)

2-2 General Information & Specifications 878595 Personal Daq User’s Manual
Note: With the use of USB hubs up to 100 Personal Daq units can be attached to one PC. With 100
Personal Daq/56 modules (each with a PDQ2 expansion module) a total channel capability of
8,000 channels can be obtained. An example of capacity calculation follows.
Calculating System Channel Capacity, An Example
Assume a Personal Daq system is comprised of the following:
• one Personal Daq/56 unit
• one PDQ2 expansion module
Using the table on page 2-1 (looking in the bottom row) we see that a Personal Daq/56 with PDQ2 can accept the
following types of channel connections:
•
60 single-ended (or 30 differential mode) for volts inputs
•
30 differential mode for thermocouple inputs
• 16 Digital I/O
• 4 Frequency/Pulse inputs
The maximum channel capacity in this set up is 80 channels. With the use of differential mode
(instead of single-ended) the maximum channel capacity is 50 channels.
In Personal Daq applications, thermocouples should not be connected single-ended. Doing
so can result in noise and false readings. This is especially true when acquiring other high-
amplitude signals in conjunction with thermocouple signals that are connected single-ended.
Features
The Personal Daq system includes the following features:
• USB connection to the PC means no batteries or other power sources required (see notes)
• signal input connections via removable screw-terminals
• high-resolution 22-bit A/D converter
• internal cold-junction compensator for direct thermocouple measurements
• 500 VDC isolation for PC protection
• low noise thermocouple and voltage measurements
• full-scale voltage inputs from –10 VDC to +20 VDC
• frequency/pulse measurements from DC to 1 Mhz
(Does not apply to Personal Daq/54)
• digital I/O with current sink capability for direct drive applications
• with addition of PDQ expansion module, up to 80 channels of analog and digital I/O are available
for one Personal Daq/PDQ combined unit (Does not apply to Personal Daq/54)
• up to 100 Personal Daq/PDQ (combined units) can be connected to one PC by the use of USB hubs;
providing a total channel capacity of 8,000 channels
• digital calibration eliminates the need for potentiometers and user adjustments
• Personal DaqView and driver software
• external power input jack for use with notebook PCs and various setups (discussed in Chapter 3)
Note 1: Certain system configurations make use of USB hubs and power adapters, as discussed in
Chapter 3.
Note 2: Some notebook PCs require that a power adapter be used with your Personal Daq.
Chapter 3 contains more information regarding power adapters.