Frequently Asked Questions
What is media & harsh media?
Media is the environment to which the sensor is exposed. Generally, this can be liquid, gas or air. Harsh media would be anything that could damage the sensor and electronics such as gasoline, oil, exhaust, water, etc.
Can I evaluate your pressure sensor products?
Yes, in fact Merit sells a TR evaluation kit (MeriTREK) that allows the end user to evaluate the TR Series fully compensated pressure sensor. The MeriTREK ships with a standard 100psi TR part but will work with any pressure range of the TR Series. In addition Merit Sensor also offers samples of other parts and bare-die for the customer to evaluate.
What is the highest and lowest amount of pressure that your sensors can measure?
Our sensors measure as low as 0.15psi and as high as 15,000psi
What are pressure sensor components?
Pressure sensor components are die or chips and simple assemblies of the same. Transmitter and transducers are fully packaged and conditioned/calibrated sensors.
What is hysteresis?
This relates to the output of the die at increasing and then deceasing pressures (or temperature cycles) throughout the pressure range or span. In general, the output is compared against itself for consistency. Hysteresis is expressed as a percent of full-scale output (FSO).
What is Sentium?®
This is a proprietary set of processes developed by Merit Sensor to achieve a wider operating temperature range, especially at higher temperatures.
What is gel?
Gel is a protective coating to isolate the die from the media. The gel is made of silicone, not to be confused with silicon. It cannot protect the die against all media.
What industries does Merit Sensor sell into?
Merit Sensor is a subsidiary of Merit Medical so we have a lot of experience selling into the medical industry but we are not limited to the medical industry. We also sell into the automotive, industrial, consumer, aerospace and defense industries.
What is an SMD?
An SMD is a surface-mountable device that can easily be picked, placed, and soldered to a substrate. The die down, wire bonding, cap attach and gelling processes have been performed.
What mediums can be measured with pressure sensors?
Air pressure, water pressure, fuel pressure, fluid pressure, blood pressure, oil pressure.
Do you design and manufacture custom pressure sensor products?
Yes, many of our customers have come to us with custom requirements and we help design a custom pressure sensor to meet their needs.
What is the topside of the die?
The topside is the electrical side of the die.
What is the backside of the die?
The backside is the cavity side of the die.
How can your HM sensing element come in contact with harsh media?
Any harsh media can be measured by a gage backside sensing element (die) so long as it’s compatible to glass and silicon. What makes the HM special is that it can also measure absolute pressure from the backside. Merit Sensor offers a variety of die bond techniques to support the harshest environments.
What is burst pressure?
This is the pressure just before the die bursts or ruptures.
Does Merit Sensor fabricate its silicon pressure sensor die?
Yes, Merit Sensor has a wafer fabrication on site at their Salt Lake City facility and produces MEMS bare die and assembled packages.
What types of pressure sensors does Merit Sensor offer?
Merit Sensor sells MEMS Piezoresistive Pressure Sensors.
What is a Piezoresistive MEMS pressure sensor and how does it work?
Piezoresistive literally means electromechanical. Pressure exerted on the sensor causes a mechanical deflection of the silicon diaphragm. In turn, this mechanical deflection (essentially the deformation of the crystal lattice structure of silicon) causes a change to the electrical properties or output of the implanted resistors.
What are the various pressure types?
Gage: pressure relative to atmospheric or ambient pressure
Absolute: pressure relative to a perfect vacuum or sealed reference - zero pressureDifferential: pressure exerted on both side of the diaphragm - the difference between two pressuresVacuum: negative pressure or pressure applied in reverse
What is a bond pad?
The bond pad is an electrical contact point where the die can be connected to a substrate.
What is bridge configuration?
This pertains to a wheatstone bridge and determines the number of connection points or pads. Bridge configurations are open (6 contacts), half closed (5 contacts) or closed (4 contacts). The performance of each is the same.
What is sensitivity?
This is the electrical output of the sensor to a specified, applied pressure. We state this in terms of microvolts per volt per psi.
What is resistance or impedance?
This is the amount of electrical resistance a circuit is experiencing.
What is a constraint?
Silicon wafers typically have a glass or pyrex support or constraint. Constraints come in gage or absolute configurations.
What is offset?
Offset is the electrical output at zero pressure.
What is TCR?
TCR or temperature coefficient-resistance is a factor used for temperature compensation. It relates to the resistance impact to the output due to temperature.
What is TCS?
TCS or temperature coefficient-sensitivity is a factor used for temperature compensation. It relates to the sensitivity impact to the output due to temperature.
What is TCZ?
TCZ or temperature coefficient-zero is a factor used for temperature compensation. It relates to the impact to the output at zero pressure due to temperature.
What is linearity?
This relates to the output of the die at various pressures throughout the pressure range or span. In general, the output is compared to a straight line. The maximum deviation from the line is expressed as a percent of full-scale output (FSO).
What is proof pressure?
This is an elevated pressure at which the die still functions.
How should the die be handled?
Die should be shipped in an electrostatically discharged (ESD) container (clamshell with wafer on tape, waffle pack, etc.) and protected against shock and vibration.
What is a waffle pack?
A waffle pack is a container that houses die that have been singulated from wafers.
How should I mount and connect to the die?
Die should be mounted with a low-hardness silicone glue. Die should be connected to a substrate using an ultrasonic gold or aluminum wire.
What should I consider when packaging the die?
Packaging-related impacts to the die can be significant. Selected impacts to consider are as follows: package materials (metal, plastic, other), filling (oil or air) and media (gas, liquid and air). Care should be exercised in these and other areas and professionals should be consulted, as needed.