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Freezing temps in a Wisconsin laboratory cause hundreds of medical tests to be discarded
Hank’s on the phone with Joe the maintenance guy at ABC Labs, a third-party medical laboratory that serves a small Milwaukee community. The city has been dealing with a polar-vortex so temps have bottomed out and the heating demands in the state are at an all-time high.
Overnight, ABC’s furnace wasn’t delivering heat consistently so more than one hundred lab tests were compromised. Lab techs are contacting the local clinics and hospitals to advise that they are unable to deliver desperately needed test results to patients. Some hospitals re-send samples. Others attempt to get the tests done elsewhere. Not only has the lab lost revenue, but lives are now at risk because of the failure of the furnace to deliver a constant temp in a dynamic environment.
Hank understands the problem and begins troubleshooting a solution.
Use the On/Off method if his application requires basic course control with an acceptable window of tolerance. This is more than sufficient and is the least expensive option.
Apply Pulse Width Modulation (PWM) where more precise control than the On/Off method is needed. This is a mid-range price option.
Apply Proportional, Integral, Derivative (PID) control where precision and accuracy are critical. This is the most expensive, but the most commonly used option. PID can be accomplished using either a VFD control or damper position control.
What Hank chooses to do is dependent upon what’s happening with the furnace. Let’s dig a bit deeper into these methods.
Hank needs a simple mechanism to manage the heating system in a home.
Mr. Jones gives Hank a call because his furnace isn’t provding the heat he and his family needs for the evening. He has set the temperature to 70 degrees but the rooms are not warming.
In this instance, course control with an acceptable tolerance is more than adequate. This is where on-off control comes into the mix.
What if Hank needed more precise control but not as much as PID provides?
Hank gets a call from a local warehouse. They need help because a duct heater in their ventilation system is not providing the heat needed for a specific room.
In this case, more precise control is required beyond the functionality that on-off control. But, the level of control needed does not require the more expensive PID method, or the equipment itself is designed to either be fully on or off. This is when pulse width modulation (PWM) variable control is the answer.
Hank needs the most precise temperature control method possible
The medical lab runs critical tests to ensure accurate results for patient diagnosis and treatment. This means that the environment needs to be precisely regulated to eliminate temperature as a variable. In so doing, the integrity of the tests can be relied upon to help save lives.
For this reason, Hank decides to use the Nano PLC’s Proportional, Integral, Derivative (PID) method for controlling the temperature in the clinic.
The table below illustrates the implications of applying each methodology using a nano programmable logic controller.
The expectation is that this, plus a deeper understanding of how each works, should provide enough insight into which methodology will work for your needs. We recommend applying only what is needed to manage costs and resources.
Select it to learn more about how it works.
