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

 

 

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The gas properties which form 

the basis for the flow 
measurement, such as viscosity 

and specific heat, exhibit a 
slight dependence on the gas 

pressure. Fortunately, this 
pressure dependence is 

predictable and can be 
corrected for in cases where it 

has an impact on accuracy 
(typically only significant for 

pressures in excess of 100 
psig). The graph shown in 

Figure 3-1 shows the expected 
span shift as a function of 

pressure for nitrogen. This 
behavior is similar for most 

diatomic gases (O

2

, H

2,

 etc), 

whereas this effect is 

insignificant for the monatomic 
gases (He, Ar, etc). This span 

shift must be considered and 
accounted for as appropriate 
for accurate flow 

measurements at high pressure 
conditions.  

There are two alarm contacts 
on the terminal strip connector within the electronics enclosure (See Section 2.8). These 

function as isolated semiconductor switches sharing a single, isolated common line. In its 
normal state each switch is “open”; when an alarm is activated the switch is “closed”.   
The meter’s processor can be configured via the digital interface to establish the internal 
condition for activating each alarm. There are many choices for internal alarms and warnings 

including overflow, underflow, or various instrument error conditions.  Each alarm can also be 
given a selectable “wait time”—a period for which it must remain in the alarm condition before 

the physical alarm is activated. See the Software Manual for detailed alarm setting and 
configuration information. 

The Hastings 400 Series flow meters can have up to eight different calibrations stored 
internally. These are referred to as gas records. These records are typically used to represent 

different gases, but they can also be useful in other ways; for instance reporting the flow in an 
alternate range, flow unit or reference temperature. The records are referred to by their 
number label from #0 – #7. The first six records are, by default, setup for the same range in the 

most common six gases as shown in Figure 2-11. If a gas other than one of these six is specified 
on the customer order it will be placed in record #6. If a second different gas is selected, it 

will be placed in record #7. If multiple different gases or ranges are specified they will replace 
some of the standard six gases. Only the gas(es) specified on the order will be verified. The 

other records will use nominal gas factors to approximate the gas sensitivity until an actual 
calibration is performed to correct for individual instrument variations. Selecting the active gas 

record can be done in one of two ways—a hardware setting or a software setting. The hardware 
setting is done by accessing a rotary encoder on the upper PC board in the electronics 

enclosure. When set to a number position from 0 to 7 it activates the corresponding gas record.  
When set to a number greater than 7, the gas record control is passed to software. If the 

software setting mode is enabled, then the “S6” digital command can be used to set the active 
gas record as shown in the example below. 

-1

0

1

2

3

4

5

6

7

8

0

200

400

600

800

1000