Chapter 1. Programming Site Data
24
DigitalFlow™ DF868 Multipurpose Ultrasonic Liquid Flowmeter Programming Manual (2-Channel)
TransFlection SIGNL Options (cont.)
Note:
Once the DF868 determines the appropriate repetition period within the limits of REP PERIOD 1 and REP
PERIOD 2, it alternates between transmits at the determined repetition period and a period that is 20%
longer. For example, if the DF868 selects a repetition period of 200 µsecs, it first transmits a series of bursts
at 200 µsecs, followed by a series at 240 µsecs. The DF868 then compares the receive signals of the first
series of bursts to those of the second series. If the two series of signals are too dissimilar, the DF868
displays an incoherent signal error.
8.
Press
[ENT]
to accept the current
XMITS Per Reading
value, or use the numeric keys to enter the desired value
(from 1,024 to 30,000) and press
[ENT]
.
This option specifies the number of transmissions used to obtain a flow rate measurement. Reducing this number
improves the flowmeter’s response time and reduces its sensitivity in poor signal conditions. The default value is
5,000.
Note:
To calculate the response time, divide the XMITS PER READING value by the number of transmissions per
second. To determine the number of transmissions per second, divide 1 sec by the repetition period. For
example, if the XMITS PER READING value is 10,000 and the repetition value is 200 µsec, the number of
transmissions per second is 5,000 (1/200), and the response time is 2 sec (10,000/5,000). Other examples
appear in Table 13.
9.
Press
[ENT]
to accept the current
Weak Signal Threshold
value, or use the numeric keys to enter a value between
0 and 100 and press
[ENT]
.
This option lets you enter an acceptable value for the two-phase threshold. When the two-phase signal falls below
this value, the
E10: WEAK SIGNAL
error message appears on the display. The default value is 20.
10.
Press
[ENT]
to accept the current
Code Length
value, or use the
[F1]-[F4]
keys to enter a value between 1 and 16.
Use this option to enter an acceptable value for the number of pulses per transmission. The default value is 8 pulses.
11.
Press
[ENT]
to accept the current
Filter Width
value, or use the numeric keys to enter a value between 8 and 64
and press
[ENT]
.
Use this option to enter an acceptable value for the number of samples of the digitized receive signal that the DF868
uses to estimate the arrival of the transducer signal. The default value is 48 (6 cycles).
12.
Press
[ENT]
to accept the current
Averaging Factor
value, or use the numeric keys to enter a value between 0
and 16 and press
[ENT].
This option allows you to enter an acceptable value for an algorithm that the DF868 uses to eliminate background
noise. The default value is 5.
Table 13: Response Time Vs XMITs
XMITs Per Reading
Repetition Rates
200 µsec
800 µsec
30,000
6 sec
24 sec
5,000
1 sec
4 sec