SensorsTechnology

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Managing Director

I live in this small city Gwalior, MP, India. I am a Physicist by education, Nuclear Scientist by Training, Electronics and Software professional by work. I am right now planning sensors and monitoring systems for water resource management and also developing technology to kill Pathogen in water / fluids by nano-second high voltage discharge pulses. Good quality drinking water is my primary concern right now. Some of our current work can be seen at www.asro.in


SensorsTechnology

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  • 04.02.2013
  • Two-wire vs. four-wire resistance measurements
  • Kenneth, I think you are talking about 4-corner measurement or you do 4-wire measurement for sensing bulk resistance in between any two pint of the film? Do you ensure film uniformity in this way? I think you will have problem if you place the probe at different points of the film with same probe spacing as space symmetry decides the similar output if thinness and its resistive properties are uniform and identical. 4-wire measurement basically assumes that there is no current flow in potential measurement, which is not true. There are limitations and that is why sub-pA currents are not measured using 4-wires. In fact adding up wires at junction points may also form thermocouples and this requires additional consideration of material selection and perhaps maintaining temperature uniformity and stability. I agree that 4-wire method generally is good for resistance and current through resistance measurement. You should also remember why current transmitters are often used in industry in place of voltage transmitters. There is a limitation on voltage carrying wires for distance and also they become noise sensitive. You also lose speed of measurement when low pass filters are added in voltage measurement path. Even though technology is age old, one still requires to read the measurement handbook many times. Perfection doesn’t come for free. Shyam www.sensorstechnology.com
  • 04.02.2013
  • LED research and where’s the money?
  • Very little information, however, a very good pointer for the future of the LED research and manufacturing. Mid IR to UV LEDs have wide range of applications and funding research is something very important and very valuable in this area. Shyam www.sensorstechnology.com/
  • 03.20.2013
  • CREE LED light bulb demo at APEC
  • It makes not much sense to say white color. It is much better to say solar spectrum match or give clear details of light output spectrum of the LED bulb along with solar spectrum. If it is RGB then in time it may also have degradation of color ratio and how spectrum and luminescence will change in time to be specified. I think price comparison may not be very wise with CFL as there are two main factor in considering replacement. 1. There may not be any UV in these LED bulbs - I just hope so. However if UV bulb with very long life can be made then it will be more worth in water and food disinfection, industrial use etc. 2. Maintenance free is worth much more and at places frequent replacement may just not be feasible and at critical time device must not fail - like in the medical surgery, airport, defense applications. I will sure give 9 out of 10 positive points for such developments. I will like to get a buld of 60W to evaluate it in my research lab to say anything further. Shyam www.sensorstechnology.com/
  • 02.07.2013
  • Who cares about EMI?
  • Right. Induced emf can cause current to flow and also induce back emf.
  • 02.11.2013
  • Rt Ct Snubber
  • In your design, the main R2C2 timing capacitor itself has number of parallel R-C networks and if you ignore the basic characteristics of the capacitor then whatever you say by adding snubber, which handles only limited 10% charge which serves little purpose and may give a very wrong idea. ESR and frequency response of C2 is something of very importance. C3 is only correcting bad performance and a wrong selection of C2 by sharing charge with delay time constant and responding to high frequencies. Here it is assumed that C3 has much higher frequency response than C2 has, which is normally may be true. First one must identify the type of capacitor is in use and what is its frequency response, ESR and residual charge properties. Shyam
  • 01.18.2013
  • Circuit's RMS output is linearly proportional to temperature over wide range
  • Marian, Perhaps matched pair transistors MAT01, MAT02, MAT03 or similar may be better choice for the linear current source. Matching transistors is very difficult when having then in separate package. Their gain matching and temperature uniformity in separate package will remain questionable.
  • 01.18.2013
  • Circuit's RMS output is linearly proportional to temperature over wide range
  • John, I agree with your comments regarding restricted use of Ohmic contact diodes 1N4148 and 1N914 in glass encapsulated form being very sensitive to light and much preferred is black plastic encapsulated diode or transistor for temperature sensing. Has anyone done a comparative study for linearity over wide dynamic range of diodes from say -55°C to +125°C range? I think, some good reference to such study will be useful. I normally use base collector shorted transistors 2N3904 or 2N3906 for 0C to 125°C range. For 1N458A from Fair child these parameters were listed but no curve at all. VR = 125V perhaps @25°C reverse leakage current 25nA and VR = 125V, TA = 150°C reverse leakage current 5uA. - Shyam
  • 01.22.2013
  • Signal integrity issues on the rise
  • I agree with above comment. It looks like a Jitter problem and if observed at far point from triggered point, then jitter may become more prominent due to signal delay adding more jitter, which is a sum of jitter from each clock pulse jitter. If clock is perfect or same clock is used for trigger then signal integrity can be seen in relative reference. Sometime clock itself has in-built jitter to have some spread in the frequency source to average out noise density in spectrum and can cause somewhat poor look in the eye/jitter view.
  • 10.21.2010
  • Circuit measures capacitance or inductance
  • By increasing Q of an inductor one is assuming that an inductor is having low series resistance of its own and such inductor can be measured with greater accuracy. This limitation remains in this design as series resistance does not get compensated for error correction. I think you have rightly pointed out. Dr. Shyam
  • 10.21.2010
  • Circuit measures capacitance or inductance
  • If Coaxial cable is of 50 Ohms RG58 type then it is to be terminated by 50 ohms to avoid reflections and pulse distortions. Some function generators may have a series resistor again for similar purpose for proper signal injection into RG58 cable. This makes a potential divider and perhaps %2 for the injected signal, hence, it is worth looking at signal across the 50 Ohms resistor that is actually used by the circuit for causing resonance waveform in the load and is used for measurement. I think this idea is simple and good one for quick measurement even though accuracy is not very high. I will give 8 points out of 10 for this idea. Dr. Shyam