Mouser signs global distribution agreement with Plessey
Mouser Electronics, Inc. has signed a global distribution agreement for Plessey's complete range of innovative products including Plessey's award winning products such as the EPIC™ sensor and MaGIC™ GaN LEDs.
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Currently the sensor is available with mid-range (flat-band) voltage gains of x10 or x50. This corresponds to around 20dB and 34dB.
The PS252xx and PS254xx family (square compact) require a bipolar supply of between ±2.5V and ±4.5V.
The PS25012x family of application boards generate the bipolar supply from a single supply, and so require only a unipolar supply of between +4 and +8V.
The PS251xx family of sensors require only a unipolar supply between +4.75 to +8.0V.
The PS252xx and PS254xx family (square compact) of sensors draw a supply current of around 2.5mA per sensor.
Lower current versions of the compact sensor are in development.
The PS251xx draws higher supply current − around 4.5mA per sensor.
The output of the PS251xx will swing between ±2.5V full scale. For the PS252xx and PS254xx sensors it will swing between the supply rails.
From around 50 to 100 Ohms.
The EPIC sensor detects electric fields and, because the strongest electric field in the
vicinity of the sensor is often from the 50Hz or 60Hz mains electricity supply that ambient
noise is probably what will dominate the sensor's raw output. On 50x sensors that are not
in contact with a subject, the mains frequency signal can swing from rail to rail.
For sensors with electrodes that are designed for contact sensing, the mains pick-up will reduce significantly when both the electrode and the system ground are touched.
Touching just the electrode with no ground will usually increase the mains noise as it couples through the body onto the sensor electrode. System ground contact is made by touching the metal case of PS25101 sensors or the plate on the back of the PS25012 application boards. Where sensors are used without applications boards, some means of touching the GND terminal should be provided if this method of reducing mains pick-up is being used. An alternative approach to reducing mains pick up is to employ a Driven Right Leg technique, as described in our application note Non-contact ECG measurement using EPIC.
As long as the signal is not limited by the supply rails, the required signals (e.g. ECG) can be extracted by a combination of filtering and common mode rejection (by differentially amplifying the output of two sensors). Mains frequency swings from rail to rail do not affect the ability of the sensors to detect movement, as motion will still cause a change in the measured signal. Suitable filtering should still be applied. In very noisy situations, or for measurement of non-contact electrophysiological signals, or for more sensitive movement sensing, the use of 10x gain sensors is recommended.
No. It senses through 360°, which makes it ideal for motion sensing. It is best viewed as something akin to a uni-directional microphone. A (very) small amount of forward sensitivity enhancement (really rear sensitivity reduction) can be obtained by placing a grounded metal plate behind the sensor.
The sensors are AC coupled (although the lower frequency point can be made almost arbitrarily low − typically a few tens of mHz) and so will only sense changes in the electric field. As long as one or more of the object, the sensors or the field (i.e. AC field), are moving then the object can be detected. There is no analogy to a DC baseline measurement for static field conditions.
Yes. Currently we can accurately position a human hand placed between two sensors with an accuracy of better than 10% in one dimension and around 10% in two dimensions. We can track the movement of the hand in real time, which gives the option for recognising gestures with appropriate software. See also the next question, regarding tracking moving targets, which deals with movement and gestures in larger areas.
Yes they can. The latest developments in software allow a single target to be tracked in
real-time whilst moving around an area covered by four EPIC sensors. For example a room with
one sensor placed in each of the upper corners. As the EPIC sensors track what is effectively
the "centre of charge" it is not possible at the moment to track more than one object. With an
array of sensors however we believe that this is possible.
More recent work suggests that monitoring the extant 50/60 Hz field may be a better approach for such applications (security related) and this is currently under development.
No. A highly charged (electrically) child will look like a lowly charged adult. Moreover a child close to the sensors will appear similar to an adult standing further away.
This depends on the charge on the target, the rate of motion and the local environmental conditions.
It is best to think of the EPIC sensor as being characterized by its input referred noise and its gain
rather than trying to describe a range. Adult humans can carry anywhere between zero and several thousand
volts, depending on clothing and their surrounding environment. This can mean that a moving human target
is detectable from say a metre worst case, up to several metres best case.
Recent developments suggest that maybe it is best not to measure perturbations in the quasi DC field but to use already existing AC fields that surround us in our normal day to day life. For example 50/60 Hz signals Using changes in the detectable signal strength amongst an array (or even between a pair) of electrodes it may be possible to locate targets at a greater range and with more reproducibility.
Yes − in some circumstances. If the sensor is placed close against an interior wall then it is possible (but not guaranteed) that electrical activity can be detected on the other side. If the wall contains metal or is in itself conducting then this may act as a Faraday Shield and render detection impossible.
No. The upper frequency detected by currently available sensors is in the tens of kHz range. RF signals, including those from mobile phones are much higher than this and so do not disrupt the EPIC signal.