Omega Engineering OMB-DBK-34A, User Manual

Page: 164 / 250

Hardware Setup
DO NOT adjust the potentiometers! Evidence of adjustment voids the factory warranty!
Card Configuration
DBK15, pg. 2
889094
DBK Option Cards and Modules
Factory Default:
Input range of ±5V
1. Determine the LogBook’s or Daq device’s Analog Input Channel for each DBK15
in your system. As few as one or as many as 16 DBK15’s may be connected to
your device. Since this is a daisy-chain type interface, each card must appear
unique. This is accomplished by assigning each card to a different Analog Input on
the LogBook or the Daq device.
2. Locate the 16×2 pin header labeled JP1 near the front of the board. Note the 16
jumper locations on this header labeled CH0 through CH15 corresponding to the
LogBook’s or Daq device’s Analog Input Channels.
3. Set JP1 jumper on the pins for your intended output channel (CH0-CH15, see
figure). Only one jumper is used on a single card. No two cards in the same
system can have the same jumper setting.
4. On enhanced versions of this board, bias resistors have been installed between the channel lows and
analog common. If you have an early version of the board, you can still install bias resistors. The use
of bias resistors is discussed in the
Signal Management chapter.
5. Determine values for R
A
and R
B
for each input signal channel. Standard RN55D (¼ watt, 1%, metal
film) resistors or 22 gage bare wire (short) plug in pin sockets. See the following table.
Note that a multiplexed input in sampled data systems must have low impedance to allow for
accurate measurements. For 12-bit accuracy at 100 kHz, equivalent attenuator impedances should be
less than 1 k
Ω
and signal sources must have impedances less than 1/4000 of the attennuator input
impedance. For example, a 2:1 attenuator using 2 K
Ω
resistors will have 1 K
Ω
of equivalent
impedance; but the source impedance must be less than 1/2
Ω
(1/4000 of 2000) for 12-bit
measurement accuracy to be attained.