
ZENO
®
-3200 USER MANUAL
Coastal Environmental Systems (206) 682-6048
Page 151
Due to their fine, as opposed to coarse, resolution 18-bit ADC measurements
are highly susceptible to noise. A single 18-bit ADC measurement is
generally only accurate to 15 bits. To obtain 18-bit accuracy, at least 3
consecutive measurements must be made by setting Line Item #10, the
Sensor Sample Count, to 3.
Three consecutive 18-bit ADC measurements will require a minimum of 300
milliseconds.
Because the baseline voltage range of the 18-bit ADC is so small, extra electronics are available on the
ZENO
®
-3200 to attenuate or provide a gain to the inputted analog voltage. Together the gain and
attenuation greatly extend the available voltage range of each 18-bit ADC sensor type, either single-ended
or differential.
To configure an analog sensor, you will need to configure 3 line items in the Sensor Record for a 12-bit
ADC sensor type or 5 line items for an 18-bit ADC sensor type:
Line Item #1: Sensor Type
Line Item #3: Channel
Line Item #4: Analog Channel Gain (18-bit ADC Only)
Line Item #5: Analog Channel Attenuation (18-bit ADC Only)
Line Item #17: No. of Additional 15-msec Delays
To configure Line Items #1 and #3, use the following table:
Sensor Type Available Channels
(Line Item #3)
Code
(Line Item #1)
Name
Internally Connected
Externally Connected
1 12-bit ADC
Internal Temperature Sensor,
Battery Voltage, GND
8 or 9
2
18-bit Single-Ended
ADC
GND
1- to 7-,
1+ to 7+
3 18-bit Differential ADC GND 1 to 7
If your ZENO
®
-3200 is equipped with one or more optional Analog
Expansion Boards (up to four), then the total number of available channels
is greatly increased!
Each Analog Expansion Board supports up to 16 single-ended analog
channels or up to 8 differential analog channels.
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