MODEL YB8 PROGRAMMING SECTION
April 1999/Manning Environmental Inc.
3DJH%
Analog Option Programming
This section explains how to program the sampler if the unit has the optional analog controller. If it was not
ordered, it is not necessary to read this section. The analog option allows the sampler to accept an analog
signal (4-20mA) from an external device.
When using any o f t he analog programming Modes ( *05,*06, *09, *11, and *13), the sampler will prompt t he
user to enter an upper and a lower limit. T hese limits can refer t o flow or level depending on the program.
The limits are important because of the Analog to Digital converter in the YB8. The converter allows an
analog signal to be divided into 256 (0 to 255) divisions which digitizes the signal. The lower limit will
correspond to the lowest signal level (4mA in 4-20mA, etc.) sent from the external
device. T he higher limit will correspond to the highest signal level ( 4-20mA) sent from the external device.
T he difference between t he lower limit and the higher limit is t he span.
The processor divides the span into 256 evenly spaced steps.
For example, with a 4-20mA signal, if yo u set the lower limit to equal 4 ft and the upper limit to equal 44 feet
the following values would automatically be assigned to each:
Analog Signal Level A/D Digital Value
4mA 4ft. 0
8mA 14ft. 63
12mA 24ft. 127
16mA 34ft. 180
20mA 44ft. 255
Totalizing
When the volts or amps of a signal vary, corresponding to a flow, then the signal can be used to totalize the
flow. Each time the analog signal is read, a value is obtained that can be converted into a flow. For example,
(using a 4-20mA signal) when the analog signal is 12mA, then we know that the flow rate is half of the total.
If maximum flow is 100 and minimum is 0, then the flow rate is 50. The volume units of the number are
determined by the volume units of t he maximum and minimum flows. I f t hey are in liter then the flow is in
liters, if t hey are in gallons t hen the flow is in gallons. Flow is volume per unit t ime, and though t he volume
unit can be anything the time units cannot. E xcept fo r 1 condition t he flow unit should be volume unit per
minute (gallon/min, L/min, etc), and the interval to check the analog signal should be 1 minute. The exception
is when the sampling sequence (time to take and deposit a sample) takes longer than 1 minute. In this case,
the time interval between analog signal checks must be increased. When the time interval between analog
signal checks is greater then 1 minute, the volume that triggers a sample must be divided by the value of the
time interval to function properly.
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