Fluke 5686, Руководство пользователя

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Glass Capsule Standard Platinum Resistance Thermometer
Specifications
5
Specifications
Table 2. Specifications
5686 Specifications
Temperature range –260 °C to 232 °C
Nominal R
tp
25.5
Ω
Resistance ratio W(302.9146 K) ≥1.11807, W(234.3156 K) ≤0.844235
Drift rate over the entire range <0.005 °C per year
Drift rate over a range of 100 °C Typically 0.001 °C per year
Filling gas
Pure helium (99.999 %)
Lead wires Four platinum wires, 3 cm long
Diameter (mm) 5.5 ±0.3
Length (mm) 56
Construction
Construction of the 5686 SPRT is shown in Figure 2. The 5686 covers the range from 13 K to
505 K. The 25.5 Ω sensor element is crafted using high purity platinum wire wound in a strain
free design on a fused silica cross frame.
Glass Sheath
Platinum Helix
Platinum Lead Wires
Glass-Platinum Seal
Sensor Support
5686.eps
Figure 2. The construction of 5686 SPRT
Installation
Environmental Issues
Primary standard equipment should be used in a calibration laboratory or other facility
specifically designed for this purpose. Environmental requirements include:
• Stable temperature and humidity
• Clean, draft-free area
• Low noise level: low radio frequency, magnetic or electrical interference
• Low vibration levels
Mounting
Capsule-type SPRTs are usually used “totally immersed”, meaning that they are generally inserted
into a well in a copper block. The connections are made to long fine copper wires insulated with
varnish or a similar coating, and these are thermally anchored to the block and to at least one
other point within the cryostat so as to reduce or eliminate heat flow into or from the thermometer.
For applications above 100 °C, the user should decide how to mount the capsule in his apparatus
according to the conditions.
Electrical Circuit
The 5686 SPRT is equipped with four platinum wires with Teflon sleeves. Four lead wires are
used to cancel lead wire resistance. For best results, the readout device should be equipped to
handle four-terminal resistors. The lead wire colors are red and black. Two red color leads are
from one end of the sensor resistance, and two black leads are from another end (See Figure 2).