Athena III User Manual Rev A.03
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inputs is that only half as many are available because two input pins are required to produce a single differential
input. Athena III can be configured for either 16 single-ended inputs, or eight differential inputs, as shown below.
The default setting is single-ended mode.
If you have a combination of single-ended and differential input signals, select differential mode. To measure the
single-ended signals connect the signal to the plus (+) input and connect analog ground to the minus (
–) input.
WARNING:
The maximum range of voltages that can be applied to an analog input on Athena III without
damage is ±35V. If you connect the analog inputs on Athena to a circuit whose ground potential plus
maximum signal voltage exceeds ±35V, the analog input circuit may be damaged. Check the ground
difference between the input source and Athena III before connecting analog input signals.
7.5.2
Unipolar/Bipolar Input Settings
The analog inputs can be configured for either unipolar (positive input voltages only), or bipolar (both positive and
negative input voltages). For unipolar inputs, install a jumper as shown below. For bipolar inputs, omit the
jumper. The default configuration is bipolar mode (jumper out).
A/D Unipolar/Bipolar Selection
7.5.3
Analog Output Configuration Settings
The four analog outputs can also be configured for unipolar (positive voltages only) or bipolar (both positive and
negative output voltages). In unipolar mode, the outputs range between 0-10V and the outputs reset to the
bottom of their range (zero-scale). In bipolar mode, the outputs range between ±10V and the outputs reset to the
middle of their range (mid-scale).
Normally, the D/A is configured to power up to 0V. When the power is turned on, the device connected to the
analog output does not see a step change in voltage. Therefore, for unipolar mode, the outputs should normally
be configured for zero-scale reset, and for bipolar mode the outputs should be configured for mid-scale reset
because 0V is halfway between -10V and +10V, for the ±10V range.
The analog output configuration is set in software using the DACPOLEN and DACPOL registers. DACPOLEN
must be set to 1. Then DACPOL can be used to set the analog outputs to unipolar (DACPOL = 0) or bipolar
(DACPOL = 1) mode.
A/D Single-ended/Differential Selection