Quick case history: Yes, a few companies still make custom instruments
For the entire 40 years that Moore Industries has been in business, it has built “specials” for customers. As soon as its first six signal conditioners hit the market in 1968, requests started coming in for custom inputs and outputs, different temperature ranges, special mounting brackets and more.
Old-time instrument people may remember that this is the way most instrument companies operated in the ’60s and ’70s. Building specials was how we all met the needs of customers; and, because most companies that sold instruments in the U.S. also built products in the U.S., it was fairly easy. After all, development engineers and manufacturing operations were in the same building.
Over the years, many instrumentation companies have been acquired by conglomerates, or merged into massive organizations. With that, they outsourced manufacturing and lost the ability to build specials. After all, it is very difficult to build a special when the product is being manufactured on the other side of the world. Because Moore Industries still builds its products in a factory near Los Angeles, we can still do it. The result is we’ve built more than 10,000 specials in recent years, and many of those special modifications have found their way into our products as options, or have became new products.
Such was the case with our HTZ Smart HART Humidity and Temperature Transmitter, which we released as a new product in March 2008.
From special to product
Specials often come about because somebody has a problem that can’t be met by an off-the-shelf device. In this case, semiconductor companies were experiencing problems with their primary suppliers of humidity instrumentation because they could not measure dewpoint accurately. Some semiconductor processes require measurement of dewpoint to an accuracy of 0.5 °F, and no instrument on the market could provide such accuracy.
Integrated circuits that have been exposed to moisture can become weak and break when being mounted on printed circuit boards. High moisture can increase the conductivity of permeable insulators, cause corrosion in electronics, or increase back-out times. Low humidity may make materials brittle or cause electrostatic discharge (ESD).
Measuring humidity was not the answer, because relative humidity is a measure of the amount of water in the air compared to the amount of water the air is capable of holding at that temperature. Dewpoint measures how much water vapor is in the air. Because condensation can cause so much damage in semiconductor manufacturing, it is vital that the temperature in a clean room never drop to the dewpoint or lower, because water will condense onto circuits. Moreover, in some semiconductor processes, the temperature must be maintained to accuracies as small as 0.1 °F. Therefore, semiconductor companies typically need very precise measurements of temperature and dewpoint.
Temperature accuracy was the biggest part of the dewpoint problem. Most humidity transmitters measure only humidity. The key to determining dewpoint is to make very accurate humidity and temperature measurements, and then calculate dewpoint from those measurements. The semiconductor manufacturers’ solution was to install a separate high accuracy temperature transmitter next to their expensive humidity transmitter, and then make their own calculation from the two measurements. In many cases, the companies were using our TRX temperature transmitter to obtain the accurate temperature measurement. However, using two instruments simply added cost.
What the semiconductor industry needed was a reasonably-priced, all-in-one instrument that measured humidity and temperature, and calculated dewpoint with high accuracy. They also needed HART capability and a local display. No instrument on the market had all these capabilities. One large semiconductor company in California, who had been using dozens of TRX temperature transmitters, asked if we could develop that ultimate device.
Moore Industries worked with three semiconductor manufacturers and six engineering groups in the semiconductor industry for more than two years to develop exactly what they wanted. Essentially, we combined our temperature technology with a humidity sensor that met all the accuracy requirements, and worked on coming up with the exact physical configuration needed.
Once the development was underway, more detailed requirements emerged:
The temperature and humidity sensors had to take air samples from exactly the same place. After much deliberation, we decided that two probes placed side by side was the best solution.
The customer required frequent calibrations, so the dual probe was designed so that either sensor could be removed for maintenance or calibration without disturbing the other.
During calibration and maintenance, the outputs had to hold the last value so alarms within the HVAC control system wouldn’t be activated. Therefore, the HTZ maintains its two current outputs at a predetermined value while either sensor unit is taken out of service.
The HTZ includes a sensor module that holds the probes and a display module that gives local indication while providing two loop-powered analog outputs. The sensor module can be mounted on any surface or pipe, such as an HVAC duct or a clean room wall. The display can be mounted up to 30 ft from the sensor module. The user can determine what variables — temperature, humidity, or dewpoint — are represented by the two 4-20 mA signals, and use a HART monitor to obtain all of the other digital signals, such as the third process variable, status, diagnostics, and other relevant information.
After building and testing several prototypes, we installed them at semiconductor plants next to existing humidity and temperature systems. This allowed us to compare the results from the two systems. After that field testing, we developed the final configuration of the HTZ.
During this development process, we researched the need for dewpoint measurements in other industries, and discovered that biotechnology, food, tobacco and pharmaceutical manufacturers also use dewpoint as a process variable. In pharmaceutical manufacturing, for example, increased humidity causes fine powders to adsorb moisture, sometimes clogging the powder feed to a tableting press, and inconsistent powders from fluctuating moisture content can cause crumbling tablets. Polyvinyl pyrrolidone (PVP) is used in many bioengineering and pharmaceutical applications, and its adhesion characteristics are affected by changing humidity.
After successfully engineering, manufacturing and supplying the original customer an application specific special instrument, we determined that this combination device filled a widespread need across multiple industries. Hence, another special solution became a standard product.
Carl Barnett is senior application engineer, Moore Industries-International .
—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
Control Engineering Process Instrumentation & Sensors Monthly
Register here and scroll down to select your choice of free eNewsletters .