Liquid Controls SP2900 - Manual (Page 14)

4-20mA Square Law Table
mA Input Pulse/Sec mA Input Pulse/Sec
4 0000 10 6123
5 2500 12 7071
6 3535 16 8660
7 4330 18 9354
8 5000 20 10000
To calculate the Pulse/Sec for a particular input use the
following formula:
mA - 4 x 10000 = # Pulse/Sec to Processor
16
EXAMPLE: To calculate the Pulses/Sec for 9mA Input.
9 - 4 x 10000 = 5590 Pulses/Sec to Processor
16
CALCULATING THE K- FACTORS
The analog inputs are converted to a highly linear 0 to
10000 pulse per second frequency. The high level of any
analog input will generate this 10000 Hz frequency. The
pulses go directly to the central processor. The K- Factors
are used to convert the pulses into the correct units of
measurement.
Rate K- Factor: 10000/R, where R = high output rating
(20mA or 5V) of transmitter. 10000 divided by 20mA or 5V
rating of transmitter. Eg. 20mA rating of transmitter is 250
gal. per min. The rate K - Factor to key into the unit for gal.
per min. is 40 (10000 divided by 250).
If a rate is desired in a different unit of measure or a
different timebase, factor the transmitter rating to the unit of
measure and timebase desired and use the formula above.
Eg. 5V output rating of a transmitter is 300 gal. per min.
and rate desired is liters per hr. The factored rate for this
transmitter for liters per hr. is 68135.94 (300 x 3.78533 [gal.
to liters] x 60 [min. to hr.]. The rate K - Factor for liters per
hr. is 0.1467654 (10000 divided by 68135.94).
Counter K-Factor: = 10,000/R/Sec, where R = High output
rating (20mA or 5V) of transmitter factored to rate per
second. Eg. 20mA rating of transmitter is 500 gal. per min.
Rate per sec. is 8.3333333 (500 divided by 60). Counter K-
Factor to key into unit is 1200 (10000 divided by
8.3333333.
If a different unit of measure is desired, factor the given
transmitter rating to the desired unit of measure in units per
second and use the formula above. Eg. 5V rating of trans-
mitter is 250 gal. per hr. and it is desired to totalize in liters.
Rate in liters per second is .2628701 (250 x 3.78533 [gal.
to liters] divided by 3600 [hr. to sec]). Counter K-Factor to
key into unit to totalize in liters from 250 gal. per hr. trans-
mitter is: 38041.603 (10000 divided by .2628701).
ANALOG INPUT EXCHANGE/CALIBRATION
If an analog sensor cannot be obtained that matches the
unit input, it is recommended that the unit be returned to
have the analog input module exchanged and recalibrated.
Recalibration should only be attempted by someone who
has the equipment to generate a very accurate low and
high signal and who has the training to open the unit and
work with grounded equipment necessary to protect the
static sensitive CMOS circuitry.
Set the ratemeter as follows: K Factor = 1, sig. fig. = 6,
window = 02 and the weight = 0. See the section “Remov-
ing the Case” to get at the analog input card, mounted just
behind the display. There are two pots that set the “0”
(R3) and 10000 Hz (R15) frequency. R3 and R15 are
silkscreened just under the .3 inch square pots. While
inputing a very accurate high input signal. Set R15 so that
the display reads 9999 to 10000. Remove the input signal
and adjust R3 so that the display reads “0”. Readjust R15
until it is as close as possible to 10000. Go back and
readjust R3 to insure it is at “0”. Repeat this procedure
untill both the "0" and "span" pots are set properly.
RESET
REMOTE
The reset is positive edge active; once reset, the unit will
accept new data even if reset is held. Applying a 3 to
30VDC pulse of minimum 5 msec resets the batch counter
and control output. Impedance 10K to ground (-DC).
FRONT PUSH BUTTON RESET
Pressing the front CLR button will reset the control output
and any displayed number (load the “Preset A” number into
the display if “SP”, subtracting mode of operation, has been
selected).
AUTO RESET
To recycle the unit, choose the preset which is to activate
the reset and set it’s “Relay Duration” as short as possible.
Place a 10K Ohm resistor between reset (Pin 5) and the
chosen transistor output for the preset chosen (Pin 19 or
Pin 20). The relay acts as a pull up resistor and the unit
resets after the control output “times out”. After the unit is
reset it will operate even though the reset is high. The reset
is edge triggered and only resets when the input goes high.
Note that if Pin 5 is pulled high by a resistor, it must be
pulled low a min. of 5 msec and then allowed to go high to
reset the unit.
FACTOR/”DATALOST”/”RFFF...”
The K- Factor is used to convert the frequency generated
internally by the analog input to engineering units. The 8
digit K -Factor dividers, with decimals keyed into any
position by use of the “D” button, allows easy direct entry of
the desired K - Factor. A separate K - Factor may be
entered for the count and rate section. Thus you may batch
and total in gallons and display rate in liters per hour.
NOTE: If the counter K - Factor is .0001 or less or if the
factored count speed exceeds 20000 CPS, “DATALOST”
flashes. If the input divided by the rate K - Factor exceeds 7
digits “RFFF...” flashes. These alarms indicate that the
factored speed has been exceeded and data is invalid.
Increase the K - Factor divider.
√
√
12