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Faq

Q: Does Phoenix America Inc. manufacture custom proximity and speed sensors?
A:
Absolutely. In fact, most of our sensor business is custom in nature. Here are a few examples of custom products we're designing and building:
 
      • Rotary position sensors
 
      • Magnetic encoders 
     
      • Ignition timing sensors
  
      • Single-chip magnetic speed & direction
         sensors    
 
      • Dual-chip programmable speed &

        direction sensors

 

 
Our engineering staff exists to meet the needs of OEM sensor customers, so we're equipped with all the necessary customization and prototyping tools, including magnetic modeling, stereolythography, and a qualification test lab.
 

Geartooth Sensors Feasible Target Shapes and Materials

 
Q: I don't have a gearwheel target, but I'd like to sense the travel of a ferrous roller chain. Is this possible?
A:
Yes. Although we commonly call them "geartooth" sensors, Phoenix America Inc. speed sensors can sense the      rotation or motion of a variety of discontinuous shapes, provided that the target is ferrous. In addition to gears, feasible targets can include roller chains, bolt heads, sprockets, and cavities in a smooth surface. Of course, the shape of the target, the height of the teeth, the pitch of the teeth and other factors all influence the feasibility of the target, so if you're uncertain, give us a call. Our engineering group will be glad to help you optimize your magnetic and electrical circuits. If you prefer to use a ferrous target and need help with supplying one, Phoenix America Inc. also can supply gear tooth target or custom ferrous targets.
 
Q: How do I know whether my target is a suitable material for use with a geartooth sensor?
A:
A feasible target needs to be ferrous, so a good starting point is to check whether a magnet sticks to it. The ideal material is a low-carbon cold-rolled steel.
 

Sensing Direction and Speed

 
Q: Can Phoenix America Inc. speed sensors tell me which direction my target is spinning?
A:
There are a couple of different answers to this question, depending upon your target and your requirements.
 
If your target is a regular gearwheel, then a Phoenix America Inc. Series Speed & Direction sensor will provide you with both speed and direction output. This is possible because the Speed and Direction sensor has two Hall effect IC's inside, slightly offset from each other. Internal conditioning logic analyzes the phase difference between the two sensors to determine the direction of target rotation. Of course, two single-chip sensors can also be used to provide phase information to your processor, which can then calculate direction of rotation, but then you'd have to buy two sensors.
2. If you're looking at a high-volume program, you might also want to consider utilizing a Phoenix America Inc. multi-pole magnetic wheel as your target. With a Phoenix America Inc. Magnetic wheel target, we can interface a standard or custom speed and direction sensor that can be quite economical compared to typical geartooth sensing solutions.
 
Q: How does a Phoenix America Inc. speed and direction sensor give me directional info?
A: The standard Speed and Direction sensors has two separate digital outputs. It uses an open collector (sinking) output, so the speed output switches from high (Vcc) to low (close to zero) when it sees a transition from "no-tooth" to "tooth present". The separate direction output is high when the gear rotation is clockwise and low when the gear rotation is counter-clockwise.
     Of course, if you are on the other side of the gear, then clockwise becomes counter-clockwise.
 

Airgap between target and sensor

 
Q: How far away should I place the sensor from my target?
A:
Unfortunately, there's no standard answer to this question because the appropriate distance is target-dependent. In general, smaller gearteeth drive the need for a smaller airgap, and larger gearteeth allow for larger airgaps. As a ballpark rule-of-thumb, consider starting with an airgap of .040" to .080" (1 to 2mm). Feel free to call Phoenix America Inc. engineering department to discuss how the features of your proposed target can influence appropriate airgap.
 

Frequency

 
Q: What's the maximum operating speed of a Phoenix Speed Sensor?
A: This is somewhat dependent on the target and the particular sensor you choose, but the maximum frequency is generally >10 kHz. Care must be taken in calculating the frequency, depending on target geometry. With asymmetrical targets, say ones with narrow tooth widths compared to tooth gaps, the time between the leading and trailing edge of the tooth is generally the governing factor. Our sensors have maximum response times of approximately 10 mS to 50 mS due to internal Hall cell processing schemes. If your response time is close to these numbers, unexpected results, such as lost counts, can occur.
 
Q: What's the minimum operating speed of a Phoenix Speed Sensor?
A: As opposed to the Phoenix America Inc. 5900 series Variable Reluctance sensors, a Phoenix America Inc. 5700 & 5800 Series geartooth sensor has an output amplitude that is independent of input frequency. This means that it does not require any minimum speed. It does, however, require some initial movement of  the target in order to locate the tooth edge. That's why we prefer to call it a "near-zero-speed" sensor, whereas some folks refer to similar products as "zero-speed" sensors. 
 

Orientation

 
Q: When I mount a Phoenix America Inc. geartooth sensor, do I need to worry about the rotational orientation of the sensor?
A:
No, the Phoenix America Inc. 5700 & 5800 Series geartooth sensors are not orientation-sensitive. The Phoenix America Inc. Series speed & direction sensors do have an orientation requirement, and the appropriate orientation is noted on the part itself.
 

Operating Life

 
Q: What's the expected operating life of a Phoenix America sensor in terms of number of operations?
A:
Phoenix America Inc. sensors are a solid state devices with no moving parts, so its operational life is virtually unlimited.
 

Output of Phoenix America Inc. Solid State sensors

 
Q: If I have a geartooth sensor with a sinking output, will the output voltage drop when a tooth is present, or when a tooth is absent, or only in the transition from absence to presence, or what?
A:
A Phoenix America 5700 & 5800 Series geartooth sensor could be described as an "edge detector" or a "gradient sensor" or a "differential sensor". All of these terms are trying to describe that the sensor does not sense the face of the geartooth, but rather the transition from tooth to no-tooth (or vice-versa). This means that when you initially power-up the sensor, the sensor will be idle until it sees the first transition between tooth and no-tooth. With a sinking output, the transition from no-tooth to tooth will cause the output signal to switch from VCC to VSAT (for example, with a 5vdc supply, the output would switch from 5vdc to less than 700mV). A nice feature of this "edge detector" sensor is that it is self-adjusting. This means that it can adjust to worn gears, imperfect tolerances, and gear wobble.
 
Magnetic Proximity Sensors
 
Magnet poles
 
Q: Does it matter whether I use a North Pole or a South Pole to operate a Phoenix America Inc. magnetic proximity sensor?
A:
It depends on the sensor. Most of the solid state sensors in our standard product line are sensitive only to the South pole of a magnet. The following can be exceptions for a custom product:
 
    • Sensors using GMR sensing elements and which are 
       omnipolar. This means that they can be activated by either a North
       pole or a South pole.
 
    • Devices using bipolar latching sensors. They are latched with a
       South Pole and unlatched with a North pole.
 
    • Devices which includes both North pole-sensitive devices and 
       latching devices.
 
    • All of the reed sensors, which are omnipolar.
 
Air gap between magnet and sensor
 
Q: How far away should my magnet be in order to operate a magnetic proximity sensor?
A:
There's no easy answer to this question because it depends on your magnet. In general, we can tell you that nearly every user of magnetic proximity sensors employs an airgap of less than 1 inch. The majority uses an airgap of less than ½ inch, and an airgap of ¼ inch is typical. Having said that, you really need to evaluate the magnet and the sensor in order to assess the appropriate airgap for your application. Phoenix America Inc. engineers can help you model your magnetic circuit and can even help you select and/or design a magnet, so if you need help, please give us a call.
 
Q: Are some Phoenix America Inc. magnetic proximity sensors more sensitive than others?
A:
Most of the standard products are similar in sensitivity, but there are a few exceptions. The bipolar latching sensors, have relatively low gauss thresholds, allowing for somewhat wider airgaps. The most sensitive of all are custom desogned devices which use a highly sensitive GMR sensing element. These two devices are also omnipolar, meaning that they're indifferent to the polarity of your magnet.
 
Hall effect vs. Reed
 
Q: How do I know whether my application is better suited to a Hall effect sensor or a reed sensor?
A:
Although they are both magnetic proximity sensors, Hall effect sensors and reed sensors are significantly different in the way that they function. A Hall effect sensor is a three-wire, solid-state device whose output changes when exposed to a magnetic field. A reed sensor, on the other hand, is electrically a switch, with tiny contacts that open or close in the absence or presence of a magnetic field. In many applications, either device could be used, but there are also some situations where one technology may be preferable over the other. A Hall effect sensor may be preferable to a reed sensor if you have the following requirements:
 
    • Unlimited life. For example, if you are interested in sensing a spinning
      magnet that will operate a sensor billions of  times, you should consider
      a Hall effect sensor. Reed sensors generally have very long life 
      compared to other electro-mechanical devices, but they cannot match
      the virtually infinite life of a Hall effect sensor.
 
    • Your application can't tolerate any contact bounce. 
 
    • You're looking to do geartooth speed sensing or rotary position sensing.
      A reed sensor is restricted to binary position sensing, and it doesn't 
      function as a geartooth sensor.
 
A reed sensor may be preferable to a Hall effect sensor if you have the following requirements:
 
    • You need a two-wire device that requires no power (perhaps to
      conserve battery power).
 
    • You require immunity to ESD and have a low target price (Phoenix
       America Inc. does make Hall effect sensors with ESD immunity, but
       this costs a little more).
 
    • You want to provide a supply voltage that is outside the typical 5 vdc to 
       24 vdc supply voltage range for Hall effect sensors. For example, reed 
       sensors can effectively switch 110 vac at low current.
 
Reed Sensors
 
Q: What are you talking about when you refer to a reed sensor as "Form A", "Form B" or "Form C"?
A: This is a short-hand way of describing the contact configuration. A "Form A" reed sensor is normally open in the absence of  a magnetic field, then closes when a magnetic field is nearby. A "Form B" sensor is just the opposite - it's closed in the absence of a magnetic field and open when a magnetic field is nearby. A "Form C" sensor has three leads, which represent the normally open,  normally closed and common contacts. This is called a "changeover" device because the common contact changes from the normally
 closed position to the normally open position when a magnetic field is nearby.
 
Vane Sensors
 
Vane Material
 
Q: What sort of material do you recommend I use to operate a Phoenix America Inc. vane sensor?
A:
In order for a ferrous vane sensor to operate, the vane has to interrupt the flow of magnetic field from the magnet to the sensor, but the vane itself should not become magnetized. Low carbon cold-rolled steel makes an excellent ferrous vane.
 
Vane Position
 
Q: How deeply do I need to insert the vane in order to ensure proper function of the sensor?
A:
We recommend that your vane should penetrate to a depth that is less than .120" from the bottom of the sensor slot.
 
Opto-interrupters vs. Ferrous vane sensors
 
Q: What are the advantages of a Phoenix America Inc. ferrous vane sensor over a typical opto-interrupter?
A:
There are a few potential advantages, depending upon your application:
1. Since opto-interrupters rely on the detection of light, contamination that inhibits the detection of light can interfere with sensor  performance. Ferrous vane sensors are immune to dust, dirt and grease.
 
2. We also recommend ferrous vane sensors for their stability at high temperatures. Phoenix America Inc. offers standard vane sensors with maximum operating temps up to 125C.
 
3. You should also consider a ferrous vane sensor if your sensor's ambient environment includes infrared light interference. Interfacing, Signal Conditioning, Interference
 
Obtaining usable output
 
Q: I just received a Phoenix America Inc. sensor and I can't figure out how to get a signal from it. What should I do?
A:
Phoenix America Inc.'s solid state sensors use sinking and sourcing interfaces. For sinking interfaces, you need to select an appropriate external pull-up resistor, and for sourcing interfaces, you need to select a pull-down resistor. If you have questions about connecting to your sensor, you can find information about outputs and connectors at
 
ESD
 
Q: Are Phoenix America Inc. sensors ESD sensitive?
A:
The answer depends on the sensor type.
1. Phoenix America Inc. reed sensors and Variable Reluctance sensors are not solid state devices, and they're immune to ESD.
 
2. Custom devices equipped with additional circuitry to enhance ESD immunity have been tested through our users in accordance with IEC publication 1000-4-2 using test standard  EN50082-2.
 
3. The standard catalog sensors should be treated as ESD sensitive and should be handled like other ESD-sensitive devices 

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