gohastings.com Hastings Entertainment Oxygen Equipment HFM-I-401 Manual De Usuario

 

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Stability – The flow meter must stabilize for at least 3 minutes at zero flow, especially 
following a high flow or overflow condition. This will allow all parts of the sensor to come to 

thermal equilibrium resulting in the best possible zero value. 

The pre-conditions required for a zero check must also be followed when making a zero 
adjustment. The zero adjustment is a digitally controlled “reset” type operation. When 

commanded, the meter initiates an internal routine that performs the following sequence: 
measure the current flow reading, store it in nonvolatile memory as a zero offset, and remove 

this value from all subsequent readings.  

This offset value can be accessed via the “S40” software query. The reported value is relative 
to an internal, un-spanned sensor voltage. As an interpretation guideline, an offset that 

exceeds 0.15 volts typically indicates that a faulty zero value is present.  
There are three different methods to activate the zero reset function--manually, digitally, and 
electrically.  
Manually – With the electronics enclosure cover plate removed, a pushbutton switch on the 
upper board is pressed.  

 
 
 
 
 
 
Digitally – A “ZRO” (“*[address]ZRO” for RS485) command is received properly by the flow 
meter’s main processor. 
Electrically – An external contact closure generates continuity between pins 8 and 9 of the 
terminal strip. 

When operating at high pressure, the meter’s performance can be affected in two distinct and 
separate ways—a zero shift and a span (calibration) shift.  

The zero offset can occur as the result of natural convection flow through the sensor tube if 
the instrument is not mounted in a level orientation with flow horizontal. This natural 

convection effect causes a zero shift proportional to the system pressure. The overall effect is 
more pronounced for gases with higher density. Normally the shift is within the allowable zero 

offset range and can be removed by activating the zero reset at the operating pressure. 

If the instrument is inadvertently or improperly zeroed, for 
example while flow is passing through the instrument, the flow 
reading is subtracted from all future flow readings.  This will 

produce large flow indication errors. 

Accessing the manual zero pushbutton requires removing the 
enclosure front plate. Care must be taken when reinstalling 
this plate to ensure that the sealing gasket is properly 

positioned and the fasteners are secure to maintain an IP65 
compliant seal.