Making the argument for wireless temperature solutions

Editor’s note: This is Part Three of three temperature articles to accompany the July Tech Update on Temperature Monitoring and Control. Part One looked at making the move from analog to digital temperature monitoring and control while Part Two investigated linking process control with building, refrigeration and environmental control systems.

Another article entitled “No spiral freezer should be an island of automation” and written for this series by Ivy Arkfeld, energy engineer for VaCom Technologies, showed how integrating a spiral freezer with process and refrigeration controls increases efficiency, speeds production and saves energy.

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Time was when your wired control network, either a proprietary DCS or more modern Ethernet-based system, could easily accommodate that extra temperature monitoring point you needed to add in your process to improve the quality of, for example, your baking or drying process. That is, provided you had a cable drop where you needed to add in a sensor, and the control software you were using would easily accommodate it. But as luck would have it, this is not always the case.

In fact, I remember a call to Omega Engineering when I worked there several years ago. A bakery plant engineer wanted to know how to go about adding temperature sensor points along the way of his 500-ft.-long tunnel oven. He felt there just wasn’t a sufficient number of data points to maintain a consistent product output quality when products changed or when environmental temperatures affected the baking process.

Part of the problem was there wasn’t an easy way of adding in one or more RTD or thermocouple inputs because the oven was not that new and didn’t accommodate additional sensor wiring. Today, this situation can be helped with wireless sensors and data concentrators—all part of a wireless—and/or IIoT network that can be interfaced with existing process control systems.

In this article, I’d like to look at what single-point solutions are available for monitoring temperature, and how a wireless solution may let you add sensor point(s) to your existing control system using data concentrators where needed. We’ll also consider how an IIoT-based monitoring system may help in fine-tuning process.

Quirky applications may need more sensor input

If you think the baker’s tunnel oven problem was a challenge, there are other applications that demand careful temperature measurement. Dan Reinarts, Rockwell Automation industry consultant describes a couple:

Consider dough mixing, where product and ambient temperature can drastically affect malleability during rolling, forming and cutting if the dough consistency is not correct. Outside temperature can cause flour and water temperatures to fluctuate significantly. PID control is typically enough to control water temperature when blending hot and cold water, but the dough temperature needs to be controlled. MPC (Model Predictive Control) is a common solution for multi-variable control. And by adding additional temperature sensors, this solution can often live in an existing control system.
Another area that often gets overlooked is temperature’s impact on bottle filling when using flow meters. Products that vary in viscosity with temperature cause a variance in the flow rate and fill time with a constant pump pressure. Because the flow rate has a direct relationship to the amount of spill, the filler setpoint is increased to compensate for this variance (fill amount = fill at cutoff + spill). To meet legal requirements, the setpoint starts off high and gradually decreases to reduce giveaway as bottle weights are measured. Using product temperature, it is possible to apply analytics to determine optimal pressure and cutoff setpoints to reduce this loss.

Justifying additional sensor points

Some years back, name-brand wireless sensor/transmitter points to measure a single temperature process variable could cost upwards of $6000 per point. Today, of course, there are less expensive solutions and methods of getting the data you need into your system, including multipoint systems. But, wired systems have their advantages, and locations where one or more sensor points need to be added, data concentrators (wired or wireless output) can get your data into a control system.

“As with wireless technology itself, sensor prices have improved dramatically,” says Nick Mecham, VP, business development, Monnit Corporation. “When Monnit began a decade ago, wireless transmitters routinely ran around $2,000; our first sensors hit the market at $49. And now, wireless sensors in our enterprise-grade ALTA line start at $77.”

“Monnit also saw a chance to make remote monitoring and the Internet of Things accessible—and usable—by all,” adds Mecham. “This is why our sensors can be up and running within 15 minutes; the way we see it, reliability and easy setup are intertwined.” Monnit offers 80-plus sensor types, including a few devices with multiple sensors. While Monnit specializes in producing single-point solutions, it can offer them at a lower price point than a larger multisensory device, however, the company offers custom-developed sensor integrations for specific needs.

“TEGAM sells a single channel wireless thermometer that includes a phone app and cloud database for $350 plus a sensor,” says Adam R. Fleder, president. A two-channel version is available for $400. Either unit can be measuring and collecting data in under 5 minutes. These units are designed for the conditions found in food processing facilities. They are highly durable and cleanable with sealed keypads for repeated exposure to food products.

For many applications, it may be important to have not only temperature information, but also level and pressure, says Robert Villarreal, product marketing manager — temperature and system products, Endress+Hauser. For such a case where multiple sensors of any type are needed, it may be more cost effective to direct the data from the sensors to a single interface—such as the RSG34/45 Memograph family—and then transmit all the data via an Ethernet or other digital protocol for remote control and monitoring. “If a temperature measurement is the only variable being monitored, for example, it may be more cost-effective to have a point-to-point solution, but those instances are becoming increasingly uncommon,” says Villarreal.

While the above solution is wired, do you need a wireless solution? “The reality is that in today’s ‘typical’ food processing plant, there’s very few practical and cost-justifiable opportunities to apply wireless temperature sensors,” says Steve Malyszko, cofounder of Malisko Engineering, a CSIA certified member. “Most food processes have numerous points of temperature sensing clustered and located in small physical areas within each plant. Ethernet-capable smart temperature sensors with copper or fiber connections provide a greater economic justification than wireless.” It’s entirely economically feasible, however, to see hybrid applications of both hard-wired, traditional temperature sensors and Ethernet-based smart temperature sensors together under the same roof of the food processor, adds Malyszko.

“Presently wireless sensors for temperature monitoring seem to be isolated to areas where temperatures are to be monitored over a large physical area such as a tank farm,” says Malyszko. Wireless can make sense from a cost-of-installation standpoint in these applications so long as security and data integrity are addressed as well.

Emerson’s Rosemount temperature transmitters offer single point measurement solutions such as transmitters with Rosemount X-well Technology, and Rosemount wireless temperature transmitters assembled to Rosemount sensors and thermowells, says Kevin Stultz, Global Product Manager, Rosemount Temperature, Emerson Automation Solutions. The Rosemount 848T wireless temperature transmitter can accept up to four independent temperature inputs and combine them into one wireless output to be received at the wireless gateway. This is beneficial when there are space constraints in the process due to high measurement density applications, and to alleviate strain on the gateway itself, as gateways have a limit to the number of inputs to which they can connect.

Before you make the move to wireless, however, you may want to check that the temperature points you are monitoring—especially if they are critical control points—will be acceptable to FDA. “What we have mostly been involved with is food processing, some more critical than others,” says Alan Clark, Palmer Wahl Instruments applications engineer. “These processes are regulated by government controls. It took the FDA from1993 to 2011 to approve the change from mercury-in-glass thermometers, which are still legal and used today, to a RTD based electronic thermometer which had to have some type of redundancy to indicate if it had a problem. About the same time, the FDA, which required a circular chart recording of every process cycle, finally allowed an electronic data logger to record that cycle if it could be printed out for the inspectors when they were there. The regulatory agencies do not trust wireless systems as something that is foolproof, and it will probably be years before they can be convinced that there would not be a potential danger to the public. It would require extensive testing along side their other systems to build lots of data for them to consider it,” says Clark.

Supporting IIoT and wireless

Wireless sensor-based IIoT has many benefits, not the least of which may be a cost advantage. “The first benefit we often see with new customers is increased flexibility for their operations,” says Monnit’s Mecham. Within production, anything that’s hardwired is semi-permanent. It’s costly to reconfigure production lines to accommodate recipe or serving-size changes or changes in market preferences. There will be wires running down to the line that have to be re-routed and reconfigured; within industry, this typically calls for electricians. The labor costs alone are prohibitive. If a user must move a line that features wireless sensors, that’s it. There’s nothing related to wireless sensors that needs to be done after the physical move.

Another benefit that helps solidify the case for wireless sensors is noise, adds Mecham. Monnit’s wireless sensors feature integrated analog-to-digital controller functions that streamline integration by eliminating the need for costly ADC analog input systems. And the wireless sensors aren’t subject to noise from power feeds, making wireless sensor accuracy more of a known entity in digital electronics than in long-wired analog electronics.

Wired systems had a cost advantage because wireless sensors used to require monthly battery swaps, but RF technology has rapidly matured. Monnit is able to get up to 12 years out of AA batteries, making them cost significantly less than running wires. This isn’t to say wireless technology is done improving. If a user is accustomed to pulling temp data every couple of seconds, wireless sensors may only provide 1–2 years of battery life. “While that’s still cost-effective, we recognize that wireless isn’t a fit for every situation—yet,” says Mecham.

Not only have sensor and transmitter costs come down, but so have their supporting equipment, starting at the I/O level. “At $750, Opto 22’s groov RIO, and other edge I/O devices like it, make real-time monitoring of multiple I/O points feasible and cost-effective,” says Joshua Eastburn, director of technical marketing, Opto 22, a CSIA partner member. As opposed to single-point data loggers with fixed memory constraints and limited or no programming capabilities for data processing and software interaction, these devices are flexible and IT-compatible. The limitation is that single-point solutions are still required for ingredient/pallet-level tracking, as edge I/O devices require an independent power source.

Utilizing edge devices or other wireless communications best fits with the critical measurement points that need to be accessed beyond the local control system, says Endress+Hauser’s Villarreal. Where a process may have thousands of instruments or control points, only a handful of them may need to be accessed from outside the plant. For remote applications that may not have access or ability to run power and communications easily, a true wireless solution would be beneficial in certain applications, such as remote storage.

Trends in temperature monitoring during transit

Maintaining temperature within a truck reefer (refrigerated trailer) really comes down to the driver—even the best are prone to bad days. Traffic or mishaps at loading docks can also affect trailer temps. Therefore, you may not want to depend on the driver for accurate temperature reporting—rather instrument your product instead.

Truck reefer temps many times do not accurately reflect what is happening with the actual product inside the container, says Emerson’s Stultz. If you do a mapping study, you will see that within a trailer or cargo container there can be many different temperature zones. “We’ve actually seen a three to five-degree difference depending on where you place a monitoring device in a 53-foot trailer,” says Stultz.

For example, the readings can be very different if the device is placed next to an air chute (where cold air is blowing), as compared to next to a trailer wall where insulation may have degraded, says Stultz. Also, it is really important that cargo is loaded correctly to promote optimal air flow. If you are only going to use one device, we recommend it be placed two-thirds back on the top pallet. Some end users deploy multiple devices—placed front, middle, and back—for increased granularity.

Recording intervals need to be adapted to the commodity being shipped, the mode of transport and the length of the shipment. “Obviously, shipping cocoa is not the same as shipping caviar,” says Monnit’s Mecham. So what’s important is being able to pre-configure reporting time intervals. Every shipment will have a different time requirement based on the density of the food, the temperature and the environment it’s being shipped through. Both Emerson and Monnit sensors offer pre-configurable sensor check-ins or “heartbeats.”

It’s probably not a good idea to rely on the driver at all for making measurements, and when these wireless devices communicate with back-end equipment (such as an edge server/controller), a lot of useful data can be obtained about shipments in transit. For example, Opto 22’s groov EPIC has been used to integrate GPS radio, WiFi, and local position sensors for mobile temperature tracking, then deliver that data on arrival without driver interaction, says Opto 22’s Eastburn. Edge devices also embed standard IT security and fault-tolerance features like user authentication, data encryption, and fail-safe file systems that ensure data is protected.

While Palmer Wahl has supplied RTD-temperature probes for refrigerated tanker trucks, the company has also created a very low-tech—but accurate—system for monitoring higher temperatures of trailers when shipping canned goods or other items less affected by temperature. “We make temperature recording labels that have specific temperature dots that turn black at specified temperatures,” says Clark. “We put those in specialized medical kits where if the pack hits 110°F, the kit has to be discarded. We make these labels from 90°F up to 500°F, and the equivalent Celsius ranges, also. The dots are accurate to within 1% of the indicated temperature and when turned, they stay, they do not go back.”

On the road again

We just looked briefly at temperature monitoring of goods in transit from a sensor perspective, but keep in mind this is a supply chain issue as well, and the Internet of Things has brought this capability within most companies’ reach today.

“IOT has made continuous visibility throughout the supply chain possible that incorporates temperature, condition, location, and context into real-time reporting,” says David Parker, chief evangelist for Cloudleaf, a high-tech supply chain system provider. “This kind of system can send alerts when the temperature starts to shift towards being out of range; notifications are set to allow for intervention before goods can fall out of a range that is FDA compliant. Reporting in general should occur at a minimum of 15 minute intervals when shipping a temperature controlled product.”

Pricing for this new technology is coming down considerably, says Parker. “Real time reporting costs about twice that of a static based logger. But the ROI from being able to intersect in time versus arriving to a destination damaged exponentially surpasses the upfront cost.”

“Remote monitoring merges static data logging with the ability to make real-time adjustments to maintain food quality,” says Monnit’s Nick Mecham. Select foods and ingredients, such as frozen items, may only need readings transmitted on exception; sensors can be configured to do that to minimize data usage for non-critical values. With other food that is more temperature-sensitive, a user may not only want a log of exceptions but a data log of values occurring through transit. Ultimately, intervals boil down to the shipped product or ingredients; they dictate the intervals necessary to configure sensors to need.

When it comes to value in monitoring shipments, Mecham certainly agrees with Parker. “We urge customers to consider the total cost of ownership when investigating transit monitoring options,” says Mecham. After crunching the numbers, many find that real-time monitoring ultimately has a much better ROI because situations can be quickly addressed during transit before substantial product loss occurs. While remote monitoring hardware may cost a little more upfront, it will be less expensive over its life when factoring in the time and product saved. This has taken on increasing importance as commodity costs fluctuate, and supply chains become stressed by external factors. Processors are being pressed to account for (and make) every penny count.

In this time of COVID-19, Emerson’s Stultz points out the value of real-time monitoring. “Our GO Real-Time Trackers are available in both single- and multi-use.” They can collect a data point as frequently as every 6 minutes, with transmission every 18 minutes. The Oversight cloud portal is used to program alert parameters. If an alert condition occurs, a warning is triggered, and the end user is alerted so they can take real-time action. End users are deploying these devices and services to track cold chain information, and to also understand location of product in transit in real-time, enabling them to determine if product will be delivered on time. This has been especially valuable to end users during the recent COVID-19 pandemic.

While not a food application, this plasma case study from Cloudleaf shows the value of IIoT sensors in monitoring critical parameters such as temperature, whether on the road or within a manufacturing campus. Cloudleaf worked with one of the largest pharmaceutical companies to integrate its continuous visibility platform that utilizes IIoT-based sensors and monitors across temperature, condition, context, and location in their newest facility. The pharmaceutical company was able to monitor down to the product level, and ultimately eliminated any losses due to temperature excursion, saving $60 million in product and prevented penalties. (See the case study in-depth here.)