Teledyne 4700 Pocket Manual page 76

4700 Refrigerated Sampler
every 10,000 gallons, you would enter 100 flow
pulses.
10,000 gallons ÷ 100 gallons = 100 pulses
If the flow measurement device sends flow rate
data via a 4-20 mA current loop instead of flow
pulses, the sampler converts this analog
current to flow pulses representative of a
volume. The sampler assumes that the current
is linear from 4 mA at zero flow to 20 mA at the
full-scale flow rate. This factory-calibrated
conversion produces one pulse every 12 seconds
(5 flow pulses per minute) at 20 mA and scales
the pulse intervals until there are no pulses at
4 mA. See Table 3-2 for flow pulse intervals at
various currents.
To calculate the number of flow pulses to enter
in this sampler programming screen, follow the
steps below.
1. Determine the full scale flow rate (Q
that is represented by the flow
measurement device at 20 mA.
2. Divide Q
the volume represented by a single flow
pulse. The time factor you choose is
determined time unit on which the flow rate
is based:
Time Unit
seconds (cfs, m3s, etc.)
minutes (gpm, l/m, etc.)
hours (gph, m3h, etc.)
days (mgd, m3d, etc.)
3-28
by a time factor (F
max time
F Factor
time
0.08333
5
300
7200
)
max
) to find