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HBLT
Manuals & Tech Data

The Hydraulic Burst-Leak Tester (HBLT) – Owner’s Manual Index

Click on the links below to download.

HBLT Software Version 1.62

HBLT Software Version 1.91

HBLT Software Version 1.93

HBLT Software Version 2.01

HBLT Software Version 2.10

HBLT Software Version 2.20

HBLT Software Version 2.31

HBLT Software Version 2.40

HBLT Software Version 2.42

HBLT Software Version 2.43

HBLT Software Version 2.44

HBLT Software Version 2.45

HBLT Software Version 2.46

HBLT Software Version 2.47

HBLT Software Version 2.48

HBLT Software Version 2.52

HBLT Software Version 2.54

Serial Cable Schematic

Hydraulic Burst/Leak Tester Upgrade Notes Index

Click on the links below to download.

Software Version 1.62

Software Version 1.91

Software Version 1.93

Software Version 2.01

Software Version 2.10

Software Version 2.20

Software Version 2.21

Software Version 2.31

Software Version 2.40

Software Version 2.42

Software Version 2.43

Software Version 2.44

Software Version 2.45

Software Version 2.46

Software Version 2.47

Software Version 2.48

Software Version 2.52

Software Version 2.54

 

The Hydraulic Burst-Leak Tester (HBLT)
Accuracy Considerations:
February 17, 2000

DEFINITIONS

Accuracy

In general, accuracy refers to the error associated with a measurement. In the case of the model 1000 HBLT, the accuracy is specified as 3 psi. This means that a reading can be relied upon to be within 3 psi of the actual pressure. (See figure 1below)

Non-Linearity

One of the components of error in a system is sensor non-linearity. The pressure sensor in the HBLT has a specified non-linearity of 0.10% full scale. In the case of the 1000 model, the sensor has a full scale of 1000 psi. A two-point calibration curve is used by the HBLT. The first calibration point is at 0.0 psi (open to atmosphere) and the second is 1000 psi. The computer in the HBLT does a straight-line interpolation and is able to derive any pressure in between. For example, if 500 psi were introduced to the inlet, the HBLT would display 500 psi if it were a perfect instrument. In reality, it might display something like 499 because the sensor really doesn’t have a straight-line behavior like the calculation assumes. In this case, the non-linearity would be: ((500 – 499) / 1000) x 100% = 0.1%

Repeatability

Another component of sensor error is its ability to deliver the same output for repeated measurements of the same pressure. The degree to which successive readings of the same pressure are different is characterized by its repeatability, which is expressed as a percentage of full-scale output. The sensor in the HBLT has a stated repeatability of 0.02% FS. (See figure 1. below)

Hysteresis

Sensor accuracy is also affected by temperature. Zero Shift means that all the readings are shifted up or down by a change in temperature. The pressure sensor in the HBLT has a zero shift of 0.01% FS per degree F. Span shift means that readings at one end of the sensor range are shifted up and the other range are shifted down. The span shift of the HBLT sensor is 0.015% FS per degree F.

Stability

Calibration must be done at regular intervals; otherwise the sensor output will slowly shift with time. This error component is referred to as the stability of the sensor. The HBLT sensor has a stability of 0.50% FS per year.

RSS

While a sensor has a number of error components, we often want a single number that characterizes the expected error. Since some of the errors could be in the same direction and others could be in the opposite direction, it would be unrealistic to simply add the error components together. It is statistically more accurate to perform a root sum square (RSS) of the components to get a realistic idea of how they might combine. This means that each error component is squared and added together and the square root is taken of the total. For example, the RSS of 1,2, and 3 would be: √((1 x 1) + (2 x 2) + (3 x 3)) = 3.74

In the case of the HBLT model 1800 (2000), the RSS of all the error components is 1.64 psi. (See chart below)

Frequently Asked HBLT Accuracy Questions

What are the sources of error in the HBLT?

There are two components in the HBLT that contribute to the total error. The first is the pressure sensor. This sensor reads the physical pressure in the system and converts it to an electrical voltage. The next component in the chain is the A/D (analog to digital converter) which converts this electrical voltage to a digital value that the computer can do calculations with. The A/D in the HBLT system contributes very little to the total error of the system. Most of the error comes from the pressure sensor itself.

What do I have to do in order to have my HBLT meet the advertised accuracy specification?

Sensor stability and thermal effects contribute significantly to the total error of the system. You can minimize these effects by operating the HBLT at a constant temperature and performing regular calibrations on the system. The stated accuracy of the HBLT assumes that calibrations are performed monthly and the system is operated in an environment that is within 5°F of the temperature at which the system was calibrated.

How can I increase its accuracy beyond the specification?

The following practices will increase your testing accuracy: Check calibration often. Calibrate at or near (but always above) the pressure you intend to do the testing at. Allow the machine to come up to operating temperature before performing a calibration or taking readings (24 hours). Use slower ramp rates. Use hookup tubing and fittings that don’t restrict fluid flow, 1/16″ (1.6mm) minimum, if possible.

Why does the HBLT 1000 and 1800 (2000) only display to the nearest PSI?

The A/D converter is only capable of resolving to 0.244 PSI on the 1000 psi model and 0.732 psi on the 1800 psi model. It would not be meaningful to display at any finer resolution than 1 psi.

Are there any conditions that can reduce the accuracy of the HBLT?

Yes. The test set up for the product being tested should be carefully considered. Be sure to use connections that have a generous inside diameter that will allow fluid to pass easily. Connect the product under test to the system in a way that doesn’t compromise its strength or allow it to leak. Be aware that small changes in the test setup will affect the results. Be consistent. Once a setup and pressure profile is established, always use the same setup and pressure profile to test that particular product.

 

HBLT Accuracy Analysis

(PSI)

(PSI)

(PSI)

(PSI)

(PSI)

(PSI)

(PSI)

Pressure Sensor 25 100 250 500 1000 3000 5000
Non-Linearity 0.100%
Hysteresis 0.080%
Non-Repeatability 0.020%
Accuracy
(RSS of above) 0.130% 0.03 0.13 0.32 0.65 1.30 3.89 6.48
Thermal / °F
Zero Shift 0.010%
Span Shift 0.015%
Total Thermal RSS 0.018%
Temp Span °F 5.00 0.02 0.09 0.23 0.45 0.90 2.70 4.51
Stability % / year 0.500%
Calibration Interval (year) 0.0830 0.01 0.04 0.10 0.21 0.42 1.25 2.08
CPU
A/D Converter
Offset 0.000%
Linearity 0.012%
Gain 0.012%
(RSS of above) 0.017% 0.004 0.02 0.04 0.09 0.17 0.52 0.86
System
RSS of above 0.04 0.16 0.41 0.82 1.64 4.92 8.21

 

HBLT User Quick Tips