Table of Contents:
Introduction
A Vaisala PTU-300 is used to monitor variations in room temperature, relative humidity (RH) and atmospheric pressure. This data will be recorded as instrument telemetry and monitored to ensure there is no correlation between instrumental shifts (spectral movement) and atmospheric pressure or room temperature changes.
Given the main spectrometer is within a vacuum chamber, the RH of the surrounding room air does not impact instrumental stability. However, extremely low RH values can affect the lifetime of electronic devices, and hence this parameter is monitored and recorded within instrument telemetry.
The Vaisala PTU300 is mounted on the chamber side of the Vac Cart. A hose connected to the pressure-measuring spigot on the PTU300 goes through the wall to measure the pressure inside the spectrometer thermal enclosure. This allows pressure within the thermal enclosure to be measured while placing the the heat source of the Vaisala itself outside in the hallway.
Relevant Devices
Description | Qty | Source | Part Number | Notes |
|---|---|---|---|---|
Barometer/Humidity Sensor | 1 | Vaisala | PTU300 | Note Vaisala now offers an ethernet interface board for the PTU300, but it has to be installed at the factory. |
Serial Interface Cable | 1 | Vaisala | 19446ZZ | Purchased separately and installed by KPF team. |
RS-232 to Ethernet Adapter | 1 | Lantronix | UDS2100 | This is the version with two serial ports (and standard 9-pin RS-232 connectors) |
Smaller Footprint Power Supply for Lantronix | 1 | Tri-Mag, LLC | Tri-Mag PN: L6R12H-120 DigiKey PN: 364-1264-ND | The stock Lantronix power supplies do not work well with the PDUs (as they block two extra outlets). KPF uses these replacement supplies since they only take up one PDU outlet. |
Relevant Functional Block Diagram
Relevant Datasheets & Manuals
Description | File | Source | |
|---|---|---|---|
| 1 | Vaisala PTU300 User’s Guide (2019 version; device purchased in 2014) | ||
| 2 | Calibration Certificates | These shipped with our actual KPF device | |
| 3 | Lantronix UDS 2100 Quick Start Guide | https://www.lantronix.com/products/uds2100/#tab-docs-downloads | |
| 4 | Lantronix UDS 2100 User Guide | ||
| 5 | Smaller Footprint Power Supply Datasheet | https://www.tri-mag.com/wp-content/uploads/2021/05/L6R12H_Series_2021-01.pdf (Linked off the DigiKey product page) |
Dispatcher Configuration File
Configuration | Value | Explanation |
|---|---|---|
ip | 192.168.23.126 | IP address of the Lantronix box. |
port | 10001 | Port that is used for Vaisala, this is port 1. |
format_str | form 9.4 "P=" P " " U6 6.4 "T=" T " " U3 6.4 "RH=" RH " " U4 \r \n | Format statement of the output from the Vaisala. At dispatcher start up and at every new connection, this value is sent to the Vaisala. The #.# sets the number of characters (first # ) and the second # sets the number of characters after the decimal point. There must be a space between the characters that notes what the value is (such as P=) and the actual value (the P). The code uses the characters (P=, RH= or T=) to determine what the next value is. |
poll_time | 5 | Time between reads of the Vaisala in seconds. |
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