This episode of Ask an Expert for industrial sensors examines and provides answers to interesting sensing questions we've received from customers just like you. We explore and answer these questions:
1. What is the slope of the output characteristic, and what is the linearity error value for inductive analog sensor NBB5-18GM60-I3?
2. Are inductive analog sensors, such as the NBB5-18GM60-I3, capable of detecting aluminum at a reduced distance, and do you have a correction factor for this?
3. Photoelectric sensor MD17/73 has a plastic retaining nut to secure it on a mounting bracket. Is it possible to order just the retaining nuts? Due to location, they get damaged or lost and we don't want to replace the entire switch.
4. Photoelectric sensor - I'm trying to sense clear fluid being shot out of a small 0.11 in. diameter hypodermic needle. What sensor, if any can detect fluid flow start and stop? The water stream is only approximately 0.09 in. in wide.
5. Thru-beam photoelectric sensor - I need to detect wire strands as they pass a sensor. The strands are less than 1 mm diameter, moving up to 5 in./s (~0.13 m/s). Is a thru-beam photoelectric sensor the best option? Which model would be best for my application?
Feel free to ask us your sensing questions, and we'll do our best to reply with the whys and hows of a particular solution.
John: Welcome to Ask an Expert! Hi, this is John Appleson, Marketing Manager with Pepperl+Fuchs. Today, I'm joined by Tracy Molnar. Tracy works as an Application Engineer here at Pepperl+Fuchs. So welcome, Tracy, and thanks for being here!
Tracy: Hi John, thanks for asking me.
John: Ok, the first question asks about the slope output characteristics of the NBB5-18-GM60-I3 inductive analog sensor. The customer would also like to know what the linearity error value is. Tracy, can you explain both of these?
Tracy: Well, first I should explain that the I3 sensor is an inductive sensor with analog output. While most inductive sensors respond with a discrete switching output when metal enters their range, an inductive analog sensor's output changes in a linear fashion as metal moves through the detection field, toward and away from the sensing face. Answers to the two customer questions can be found on the sensor's data sheet. The slope of the linear analog output, which, for this model, goes from 0 mA ... 20 mA, over the sensor's 1 mm to 5 mm range, is 5 mA per millimeter. This is also illustrated on an output characteristic curve included in the data sheet. The linearity error is listed on the data sheet as well.
John: Ok Tracy, are inductive analog sensors capable of detecting aluminum, and is there a correction factor for this?
Tracy: Yes, the specifications listed on the data sheet of inductive analog sensors are for standard steel targets, but like most inductive sensors, other metals can be detected. But, there will be a reduction factor in those cases. And for an analog sensor, this means a change in both range and in the slope of the output. Reduction factor curves for four different metals, including aluminum, are shown on the sensor's data sheet. For an aluminum target, this sensor's linear analog output goes from 7 mA... 20 mA over a 0 mm to 2 mm range.
John: Ok, this customer is asking about retaining nuts for a photoelectric sensor. Tracy, do customers have to buy brand new units if just the retaining nuts are needed?
Tracy: No. In most cases we offer replacement mounting nuts. Since these should match the size and material of the original nuts, it's best if the customer contacts us with the sensor model number so that we can recommend the correct replacement part.
John: In this next application, the customer wants to sense the start and stop of flowing water coming out of a hypodermic needle, where the opening is only a hundred and ten thousandths, and the stream is approximately ninety thousandths. Tracy, what can you suggest? Would one of our photoelectric sensors be suitable for this application, or would an ultrasonic sensor be better?
Tracy: In this application where the target is both very small and also clear, I would think an ultrasonic sensor is the better choice. Water is a good target for an ultrasonic sensor, since it does reflect sound waves, and we offer models with relatively short ranges that could reliably detect a thin stream of water.
John: Ok, here's a case where a customer is trying to sense 1 mm diameter wire strands that are moving at 5 inches per second. Would one of our thru-beam sensors be suitable, and if so, which model would you recommend?
Tracy: A target less than 1 mm is too small for most standard thru-beam sensors, but we do have a thru-beam photoelectric sensor, part of our R2 series, with a special high-precision feature. This adjustment allows the light spot to be made small enough to detect the less than 1 mm diameter wire strands in this application. In addition, the 600 microsecond response time of this sensor means the wire strands will be detected even if they move past the sensor in rapid succession.
John: Well that concludes this segment of Ask an Expert. I want to thank Tracy for joining me today, and thank our audience as well.