Tech Note 1128 Detail

Thermal Expansion Apparatus is inaccurate

Affected Products:

TD-8579A Computer-Based Thermal Expansion

Thermal Expansion Apparatus is inaccurate

PASCO Solution:

  1. Use the radius of the pinion at the point of contact with the expansion bar in the calculation or the expansion: Expansion = PinionRadius * angle[Radians], Pinion Radius = 1.323 - 1.329 mm.
  2. The pinion is clean and not slipping. Wipe the pipe and pinion with alcohol and check for moderate contact pressure.
  3. That the tube is well insulated. The tube should be completely covered with pipe insulation from one support to the other. (Early revisions of the thermal expansion apparatus included less insulation. If you have an earlier revision of the, you may contact Teacher Support for more pipe insulation or obtain more from the hardware store.)
  4. There is good thermal contact between the thermistor and the pipe. The thermistor should conform to the shape of the pipe and the spring clamp should exert significant pressure. Adding a small amount of thermal grease may help.
  5. Check that you are getting a reasonable value for the temperature. If not, you may be connected to the wrong thermistor port or have an old version of the thermistor. The current thermistors are 10 kOhms at 25 C and plug directly into the 3.5 mm stereo phone plugs on the thermistor sensor boxes. If you have a 100 kOhm thermistor, either connect it to the 100 kOhm BNC jack on the thermistor sensor box or contact Teacher Support for a 10 kOhm thermistor sensor.

Creation Date: 01/3/2011
Last Modified:
Mod Summary: