AI-TEK DH SERIES Hall Effect Sensors

AI-Tek has taken its years of experience of designing and manufacturing Hall Effect sensors for harsh applications and has developed a line of durable products for industrial, rail, military and automotive use.

The new AI-TEK DH series sensors are differential based, zero-speed, precision, single channel, speed sensors. At power-up, they calibrate themselves to the unique magnetic signature of their installed application and continue to update the calibration as the sensor is running. This unique combination of differential sensing technology and calibration make these sensors highly tolerant of installation mis-alignment, target geometry and composition, target run-out, vibration and air gap changes.

In comparison, the RH series are single-element based, zero speed, single channel speed sensors and are an excellent choice for general purpose speed sensing. Unlike the DH series that requires rotational alignment at installation, the RH series requires no alignment. Air gap adjustment is precise and easy and similar to a VR type sensor.

The new DH sensor can sense each change in target movement, regardless of speed, from near zero to 15 kHz frequency range, generating a steady pulse train of frequency proportional to target speed. Typically, each time a gear tooth (or any ferrous discontinuity) passes in front of the sensor the output changes state. This type of sensor is known as a "P" type because it uses N-P-N transistor logic (as opposed to "N" type, which uses P-N-P transistor logic).

Key Features:

Reverse voltage protection, up to -30 Vdc, to prevent damage if miswired

High temperature range of -40C to +125C

Wide range of supply voltage in single design of 4.5 - 24 Vdc

Two output options of Supply Tracking or TTL Compatible

Rugged design meeting IEC 77 Standards (European Railroad Applications)

Require special alignment

Improved duty cycle

Improved fine pitch performance

Increased air gaps

Suitable for 32 diametral pitch or coarser gear (target), the standard catalog sensors are easily applied to your various sensing needs. If you have a unique, special requirement which cannot be met with any of the standard options, we will gladly review your specs and work with you on a special sensor design.

If you would like more information and pricing about AI-TEK Speed Sensors or other AI-TEK items please contact Forberg Scientific, Inc. Customer Service.
Toll Free: 855-288-5330
Email: mechanicalsales@forberg.com

Advantages of Wika Liquid-filled Gauges

Liquid-filled gauges
Liquid-filled pressure gauges provide a number of advantages:

• The liquid absorbs vibration and pressure spikes
• The dampening action of the liquid enables the operator to
  take readings during conditions of rapid dynamic loading and
  vibration
• The liquid lubricates all moving elements, dramatically
  reducing wear in the movement
• Because most liquid-filled gauges are filled with non-aqueous
  liquid and hermetically sealed, they perform in corrosive environments
  and are immune to moisture penetration and icing
  and shock effects are lessened

Liquid-filled gauges enhance the reliability and integrity of the measuring system for long periods under extreme operating conditions.

Liquid-fill fluidAmbient Temperature Ratings (Table A)

Allowable operating range

Temperature range in which the operation of the gauge is not adversely affected by the filling liquid. At temperatures above the maximum rating, the fluid may break down. At temperatures below the minimum rating, the fluid may solidify (freeze).

Choose the right liquid

The type of liquid used to fill the gauge varies with the application. Although pure glycerine provides the best performance in most applications, each has its own requirements. Guidelines to help ensure that a fluid is properly matched to an application are:

• If icing is a problem, use gauges filled with silicone oil or other comparable liquids. They have low viscosities even at -60C
• If the system has electric accessories, such as contacts, use insulating oils
• If extreme temperature fluctuations are expected, use silicone oils

The higher the liquid viscosity, the greater its dampening capacity. The reason for this is that dampening changes in proportion to the temperature-dependent viscosity of the filling liquid. The suitable degree of dampening depends on the operating requirements the gauge must meet, such as pointer response time, pressure extremes, vibration and changes in pressure. WIKA can recommend specific liquids to suit problem applications.

Liquid-filled gauge case venting

For pressure gauges with full scale ranges of 300 psi and below (including vacuum and compound ranges of 30" Hg-0-200 psi and below), case venting (after the gauge is installed) is necessary to preserve the accuracy. Temperature fluctuations during shipment and in the process application cause the liquid filling to expand and contract which in turn increases or decreases case pressure. As a result, accuracy can be decreased and the pointer may not return to zero properly until the gauge is vented to the atmosphere.

To vent a WIKA gauge, move the valve to the open position which will release any pressure or vacuum built up in the case. If the gauge is installed in an upright position, the lever can be left in the open position. The lever allows the use of a gauge in a non-upright orientation.

If you would like to get more information about WIKA pressure gauges or other WIKA products please contace Forberg Scientific, Inc. customer service.
Toll Free: 1-855-288-5330
Email: mechanicalsales@forberg.com

Selecting a Pressure Gauge

When selecting a pressure gauge, it is important to consider the following factors to ensure safety and accuracy:

1. Pressure fluid composition
2. Pressure fluid temperature
3. Ambient conditions
4. Pressure range
5. Conditions affecting wear of the system
6. Method of mounting
7. Required accuracy

1. Pressure fluid composition
Since the sensing element of a pressure gauge may be exposed directly to the measured medium, consider the characteristics of this medium. It may be corrosive, it may solidify at various temperatures or it may contain solids that will leave deposits inside the sensing element. For pressure fluids that will not solidify under normal conditions or leave deposits, a Bourdon tube gauge is acceptable. Otherwise a Sealgauge or diaphragm seal should be used. A chemical compatibility chart follows this section to aid in the selection of the proper sensing element material.

2. Pressure fluid temperature
Steam and other hot media may raise the temperature of the gauge components above safe working limits of the sealed joints. In these cases it is recommended that a siphon, cooling tower or diaphragm seal be used in conjunction with the pressure gauge.

3. Ambient conditions
The normal ambient temperature range for WIKA pressure gauges is -40F to +140F (-4C to +60C) for dry or silicone-filled gauges and -4F to +140F (-20C to +60C) for glycerine-filled gauges. The error caused by temperature changes is +0.3% or -0.3% per 18F rise or fall, respectively. The reference temperature is 70F (20C). The correction is for the temperature of the gauge and not the temperature of the measured medium. Remote gauge mounting using a diaphragm seal and capillary line is one alternative for applications involving extreme ambient temperature. Moisture and weather effects must also be considered. Liquid-filled gauges prevent condensation build up. For outdoor use, stainless steel, brass or plastic cased gauges are recommended.

4. Pressure range
A gauge range of twice the working pressure is generally selected. The working pressure in all cases should be limited to 75% of the gauge range. Where alternating pressure and pulsation are encountered, working pressure should be limited to 2/3 of the gauge range.

5. Conditions affecting wear of the system
In applications involving severe pressure fluctuation or pulsation, the use of restrictors and/or snubbers is recommended. In addition, liquid-filled gauges increase the service life of gauges in these conditions. WIKA liquid filled gauges are generally filled with glycerine. Silicone for larger temperature extremes and Halocarbon® for use with oxidizing agents such as chlorine, oxygen and hydrogen peroxide are also available.

6. Method of mounting
Radial (LM) and back (CBM or LBM) connections are available for most WIKA gauges. WIKA stocks gauges with standard NPT threaded connections. Other types such as metric threads, straight threads, hose barbs and special fittings are available as a special order. Pressure gauges should be mounted in the upright position. For applications where the gauge is mounted side ways, horizontally or upside down, contact WIKA or Forberg Scientific Inc. Customer Service for gauge type compatibility.

7. Required accuracyWIKA stocks gauges with accuracies from ± 3/2/3% to ±0.1% of span (ASME Grade B to Grade 4A).

To ensure safe and accurate gauge selection, you must take all of the above factors into consideration. When in doubt, please do not hesitate to contact Forberg Scientific Inc. Customer Service for assistance!
Toll Free: 855-288-5330
Email: mechanicalsales@forberg.com