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Proportional Control Valve
Arduino Mega

Device Related Errors

 

Control Panel

 

Touchscreen hardware failure – Approximately 7.5% of touch screens on a widely used smart phone experienced failure within the first year [Fields 2010]. Not much other data was available on the failure rate of touch screens, however the device is cheap enough that it is feasible to have backup units ready for use in the event that this occurs. It is also important to note that a failed touchscreen will render the device unusable, so there is no possibility of this failure affecting a patient.

 

 

Hardware and Sensors

 

Faulty pressure sensor – Pressure sensors were found to have a 15% failure rate [Cadwallader 1996] due to providing a false response. The pressure sensors used in the device will be calibrated prior to assembly using known pressures, eliminating faulty pressure sensors as a potential error.

 

Pressure sensor dislodged from the cannula – If the pressure sensor becomes dislodged from the cannula tube, it will result in an open circuit which will automatically trigger the alarm. A conservative estimate is 10%, however this is simply an estimate since this system has never been used by real patients before.

 

Arduino board failure – According to the product data sheet, arduino boards have a failure rate of less than 1 part per million (PPM) over 20 years at an operating temperature of 85 oC [3]. While in actuality the error is much lower, we put a conservative estimate of 0.01%.

 

Display

 

Failure of LED for visual alarm system – 0.01% (estimated) this is a function of time, we are using the estimated rate for a new LED with 0 hours of operation [4]. The failure is not a significant problem since the speakers are the primary mode of alarm.

 

Failure of speakers for auditory alarm system – 0.01% (estimated) also extremely low, no sources found mentioned the failure rate of new speakers. To avoid this being a potential issue, implement a chime upon powering the device on. If there is no audible chime, the user will be instructed to use a different unit.

 

References:

 

[1] J Fields, A Sands, "SquareTrade Research: 26% of iPhones fail over 2 years, a Decrease from 2009," June 2010.

 

[2] L C Cadwallader, "Reliability Estimates for Selected Sensors in Fusion Applications," Idaho National Engineering Laboratory, Sept 1996.

 

[3] Arduino Mega Datasheet - Atmel ATmega640/V-1280/V-1281/V-2560/V-2561/V.

 

 

 

 

 

 

 

 

[4] Lumi LEDs, "Evaluating the Lifetime Behavior of LED Systems", 2015.

 

 

 

 

 

 

 

 

 

Touch Screen
Pressure Sensor
Alarm Speakers
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