Teledyne hfc-302 ユーザーズマニュアル

  

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Action:    Shut off all flow.  For the standard 0-5VDC output, adjust the zero potentiometer  
 

located on the upper right inlet side of the flow meter until the meter indicates zero.   

 

For the optional 4-20 mA output, adjust the zero potentiometer so that the meter  

 

indicates slightly more than 4 mA, i.e. 4.03 to 4.05 mA.  This slight positive  

 

 

adjustment ensures that the 4-20 mA transmitter is not in its cut-off region.  The error  

 

induced by this adjustment is approximately 0.3% of full scale.

 

 

Symptom:  Flow meter is out of calibration and non-linear. 

Cause:   

Leaks in the gas inlet or outlet fittings. 

Action:    Check all fittings for leaks by placing soap solution on all fittings between gas supply  
 

and final destination of gas.  Check flow meter for leaks.  Replace if required or  

 recalibrate 

as 

necessary. 

Symptom:  Little or no flow, even when the valve is in over-ride OPEN. 

Cause:   

Blocked orifice or incorrect pressure across the Flowcontroller 

Action:    Verify that the pressure drop originally specified on the instrument is across the  
 

instrument.  If the differential pressure across the instrument is correct, the orifice may  

 

be obstructed.  Remove all gas pressure and shut off power supply. Remove the valve. 

1. 

Calibration must take place with cover firmly in place. 

2. 

Connect power to “D” connector as specified in Section 

2.5.  Allow the instrument to warm up for 60 minutes with 
10% of full scale flow. 

3. 

Completely shut off the flow and wait for 2 minutes.  For 

the standard 0-5VDC output, adjust the zero 
potentiometer located on the lower inlet side of the flow 

meter until the meter indicates zero.  For the optional 4-
20 mA output, adjust the zero potentiometer so that the 

meter indicates slightly more than 4 mA, i.e. 4.03 to 4.05 
mA.  This slight positive adjustment ensures that the 4-20 

mA transmitter is not in its cut-off region.  The error 
induced by this adjustment is approximately 0.3% of full 

scale. 

4. 

Turn on gas supply to inlet of instrument and adjust the flow rate to the desired full scale 
flow as indicated by a reference flow meter/controller.   

5. 

Adjust Span pot until the indicated flow reads full scale (5.00VDC or 20 mA).  Perform this 

step only if a calibrated reference flow meter is available. 

6. 

Record flow meter/controller and flow reference outputs for flow rates of 20%, 40%, 60%, 
80% and 100% and make sure data are within ± 0.75% 3σ of full scale.  

The end cap on the inlet side must be removed to gain access to shunt assembly.  First remove power 
and shut off the supply of gas to the instrument.  Disconnect the fittings on the inlet and outlet sides 
of the transducer and remove it from the system plumbing.  Remove the four Allen head screws 

holding the end cap to the instrument.  Carefully remove the end cap, nickel gasket, spacer, and 
shunt, noting their order and proper orientation.  The shunt can be severely damaged if dropped.  

Examine the shunt.  If damaged, dirty or blocked, clean and replace as applicable.  Reassemble in the 

Fig. 4.1