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. Replacing a diffuse mode photoelectric sensor that is tied to an AS-Interface module.
2. Do you have MTTF data for the NMB1.5-8GM35-E0-FE inductive sensor?
3. Can diffuse mode sensors be used to detect metal drums in a hazardous area?
4. How to choose the correct power supply for RFID control interface unit IC-KP-B17-AIDA1?
5. Where on your website can I download AS-Interface system wiring guidelines and connection diagrams?
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: This first question asks about a direct replacement for the CP18D4DPLC diffuse mode photoelectric sensor, since it is no longer available. The customer states that he is having issues using the recommended replacement model GLV18-8-450/73/120. He further explains that the CP18 had a one output, light-on operation, and the replacement is a two output, light-on/ dark-on, which causes issues when trying to connect to the AS-Interface module VBA-4E-G2-ZA. Tracy, what solution can we offer this customer?
Tracy: The customer in this situation needed to replace an obsolete sensor. When he installed the recommended replacement there was an unexpected and undesirable result, so he figured he'd been given the wrong model. But we were able to solve the problem by changing the cordset, and here's why: The AS-Interface module the customer has can accept up to four inputs from 2- or 3-wire devices such as the CP18 sensor he'd been using. But according to the wiring diagram for the module, it can also accept up to two 4-wire sensors by distributing a sensor's dual output signals to two of the module's inputs. Since the GLV series replacement is a 4-wire dual output device, and the customer was using a 4-conductor cordset to connect it to the module, two of the module's inputs were being used instead of only one, and that didn't work for this customer. I suggested he switch to a 3-conductor cordset that would transmit only the output he wanted from the sensor to the AS-Interface module, and that fixed the issue.
John: This next customer would like to know if we have mean time to failure data for the NMB1.5-8GM35-E0-FE inductive sensor.
Tracy: Typically MTTF values can be found on our product data sheets, so that's the first place I have customers look for this information. If it's there, it will be in a section of the technical data titled 'Functional Safety Related Parameters'. As we've mentioned in other podcasts, the unit of measure for this value, a lower-case 'a', stands for 'years'. But, if this section isn't included in the data sheet, we can still help the customer find the required value. Sometimes it will be in our internal documentation, and other times, the calculation hasn't been done before, and we need to request it from quality control. That's what happened in this customer's case, but most of the time it's not necessary.
John: Tracy, this customer would like to know if we have a diffuse mode sensor that is able to detect a metal drum at a range of 3 to 4 feet. The sensor needs to be approved for a Class I, Division 2 hazardous location, and its output should be 120 VAC.
Tracy: Most of our hazardous area rated sensors are inductive sensors, which means metal is a good target. But, it must be very close to the sensor in order to be detected. And by very close, I mean an inch or two at the most for our largest, longest range inductive sensor models. If the drum is 3 to 4 feet away from the sensor, the customer will need to go with a photoelectric or ultrasonic sensor. There's only a few of those that are hazardous area rated. In fact, I can think of only one sensor and intrinsic safety barrier combination that can operate at 120 VAC. The model is OCS2000-M1K-N2, and it's a retroreflective photoelectric sensor, so we'll need to mount a reflector behind where the drum would be when it is to be detected, so that it will break the beam between the sensor and the reflector. The reflector can be up to 2 meters from the sensor, which is about 6 feet. The sensor has a NAMUR output, which is intrinsically safe and rated for up to Class I, Div. 1 locations when used with a barrier that must be mounted in a nonhazardous area. We offer intrinsic safety barriers for 120 VAC operation, which provides power to the sensor and a relay contact output for the customer's control circuit.
Tracy: The IC-KP model is a control interface for RFID systems, and the ICZ-AIDA1-MSTB is the connector for the power supply to the control unit. In order to determine the proper power supply, the customer should look at the electrical specifications of the control unit that are listed on its data sheet. This section lists a rated operating voltage for the unit of between 20 and 30 VDC, so a standard 24 VDC power supply would be appropriate. Also listed in the data sheet is the power consumption to operate the control unit itself, without read/write heads connected, and the maximum current consumption possible that includes the read/write heads being operated by the control unit. This information, along with similar data he can find on the data sheet for the read/write heads he is connecting to the IC-KP-B17-AIDA1 control unit will help him select a power supply with the correct current rating.
John: This customer is asking where he can download wiring guidelines and diagrams for his AS-Interface system.
Tracy: From the downloads section of our website, if the customer narrows his selection down to AS-Interface documents, in the English language, there are only 10 results. Of those, I think the maintenance and troubleshooting guide, and the reference and buyer's guide, are the most useful in terms of wiring. We also have a separate website, AS-Interface solutions, which links to both of the documents I just mentioned, plus how-to videos and examples to answer many of the most common customer questions and issues. Last, but certainly not least, this customer can find connection diagrams for individual AS-Interface system components on the data sheet for each item. This documentation can also be downloaded from our website.
John: Well, that concludes this segment of Ask an Expert. I'd like to thank Tracy for joining me today, and thank our audience as well.