Teledyne hfc-303-307 ユーザーズマニュアル

Changing the range of a flow controller can be done in the field, but calibration is required.  It is 
recommended however, that the unit be sent back to the factory along with the new range desired, gas 

and operating parameters. Consult factory for more information. 

The flow output signal may have noise superimposed on the 

mean voltage levels.  This noise may be due to high 
turbulence in the flow stream that the fast sensor is 

measuring or it could be electrical noise when the flow meter 
has a high internal gain (i.e. 5 sccm full scale meter).  

Varying levels of radio frequency noise or varying airflow over 
the electronics cover can also induce noise. 

Noise can be most pronounced when measuring the flow 

output with a sampling analog/digital (A/D) converter.  When 
possible, program the system to take multiple samples and 

average the readings to determine the flow rate.   

If less overall system noise is desired, a jumper may be 

installed over the pins of JP-1 on the flow measurement card. 
See Figure 2-8. Covering the pins closest to the “D” connector 
will activate a resistor-capacitor (RC) filter that has a time 

constant of one second. This will change the settling time of 
the indicated flow rate to approximately 4 seconds. Covering 

the other two pins will change the response time to approx. 1 
second. This adjustment will not affect the calibration of the 

flow meter circuit or the actual flow response to change in 
command signal (flow controllers).  This will only slow down 

the indicated response (output voltage/current). 

 

Normally, a flow controller is setup to control the mass flow.  The control loop will open and close the 

valve as necessary to make the output from the flow measurement match the input on the command 
line.  Occasionally, gas is being added or removed from a system to control some other process variable.  

This could be the system pressure, oxygen concentration, vacuum level or any other parameter which is 
important to the process.  If this process variable has a sensor that can supply an analog output signal 

proportional to its value then the flow controller may be able to control this variable directly.  This 
analog output signal could be 0 - 5 Volts, 0 - 10 Volts (or 4 - 20 mA for units with 4 - 20 mA boards) or 

any value in between. 

On the CONTROLLER card there is a jumper (JP-1) that sets whether the control loop controls mass flow 
or an external process variable.  See Figure 2-9.  If the jumper connects the top two pins, the loop 

controls mass flow.  If the jumper connects the bottom two pins, the loop controls an external process 
variable. This process variable signal must be supplied on pin 13 of the D-connector (for H pin out units) 

or pin 12 of the D-connector (for U pin out units) of the measurement card.  When the controller is set 
for external variable control it will open or close the valve as necessary to make the external process 

variable signal match the command signal.  The command signal may be 0 - 5 Volts, 0 - 10 Volts (4 - 20 
mA for 4 - 20 mA input/output cards) or any value in between.  If the process variable has a response 

time that is much faster or slower than the flow meter signal it may be necessary to adjust the gain 
potentiometer. 

The flow controller will operate normally with any command input signal between 0 - 10 Volts (4 - 20 mA 
for units with 4 - 20 mA input/output cards). If the command signal exceeds ±14 volts it may damage the 

circuit cards.  During normal operation the control loop will open or close the valve to bring the output