Description

This document compares the different types of NTC thermistors available to determine the one that aligns most closely with the thermal requirements of the FINCH CubeSat. Through initial research, it was determined that NTC thermistors would be better suited for the FINCH CubeSat as opposed to RTDs. This was because of their higher accuracy, cheaper cost, and faster response time.

Requirements

Identify the key requirements that will be used to evaluate and compare the different options being considered and how they will be weighed against one another. These criteria might include factors such as cost, performance, schedule, risk, and other relevant considerations.

  1. The thermal sensors selected SHALL be able to achieve an accuracy of at least +/- 1 Degree Celsius over the expected lifetime of FINCH (more accuracy is better)
  2. External temperature sensors selected by the thermal team SHOULD have a through-hole variant with lead lengths of at least 150 mm. However, this requirement is not stringent as the lead length can be increased in-house.
  3. External temperature sensors SHOULD cost less than $2 per sensor.
  4. Sensor research shows typical temperature range for CubeSat to be only -40 to 85 C. Therefore the sensor should at least be able to withstand temperatures within this range.
  5. The thermal sensors must be automotive grade.
  6. Pressure

Options

After extensive market research, the following candidates were found to be relevant. It is important to note that due to bulk and budget constraints, longer lead thermistor options were extremely limited. Considering that the lead constraint is not as rigorous as the other constraints, the initial two options include cheaper thermistors with shorter leads.

  1. 103JM1A (Littelfuse Inc.)

**https://www.digikey.ca/en/products/detail/littelfuse-inc/103JM1A/5230961**

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Cost/unit: 1.94 CAD

Datasheet: https://www.littelfuse.com/~/media/electronics/datasheets/leaded_thermistors/littelfuse_leaded_thermistors_glass_encapsulated_thermistors_do_35_interchangeable_jm_datasheet.pdf.pdf

  1. PX103J2 (Littelfuse Inc.)