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Table of Contents:
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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.
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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 ( |
Required Alarms
Parameter
Threshold
Notes
Time of last connection
More than 10 seconds
and standard 9-pin RS-232 connectors) |
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Relevant Functional Block Diagram
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Software Actions
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Action
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Notes
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Read pressure value
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Value reported as telemetry (see below)
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Read temperature value
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Value reported as telemetry (see below)
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Read relative humidity value
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Value reported as telemetry (see below)
Required Adjustable Settings
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Setting
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When Needed
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Notes
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Build
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Observing
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Maintenance
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Pressure measurement frequency
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Yes
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No
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Maybe
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Set in configuration file. If this needs to be changed, edit configuration file, re-install, and then restart dispatcher.
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Temperature measurement frequency
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Yes
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No
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Maybe
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See pressure.
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Relative humidity measurement frequency
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Yes
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No
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Maybe
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See pressure.
Required Telemetry
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Parameter
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Report Frequency
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Purpose
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Notes
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Pressure measurement
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Once every 5 sec [TBC]
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Environmental monitoring
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Managed through configuration file
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Temperature measurement
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Once every 5 sec [TBC]
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Environmental monitoring
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See pressure.
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Relative humidity measurement
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Once every 5 sec [TBC]
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Environmental monitoring
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See pressure.
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. |
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Relevant Functional Block Diagram
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Cable Details
Cable | Qty | Details | Notes |
|---|---|---|---|
Ethernet | 1 | Cat6 Copper Ethernet Cable M-M, 6 feet long | Entirely within Vac Cart. |
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Pictures of Devices
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Relevant Datasheets & Manuals
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As part of the KROOT distribution, there is a SerialStream interface which manages connections to and from serial hosts. This includes managing Lantronix connections.
Dispatcher Implementation
Keyword
Value
Type
RETVAL
Value returned by Vaisala.
String. The format is set in the configuration file. Only readable.
TIME
Time stamp of when the last RETVAL was received.
Unix timestamp (binary) or time stamp (ascii). Only readable.
PRES
Pressure value in units of hPa.
Double value from RETVAL, read only.
RELH
Relative humidity in %.
Double value from RETVAL, read only.
TEMP
Temperature in deg C.
Double value from RETVAL, read only.
DISP#STA
Dispatcher status.
Enum and read only. If value is 4 or “Not Connected” the connection to the Vaisala or the Lantonix is not available. If value is 3 or “Connecting” the dispatcher is attempting to connect to the Vaisala through the Lantronix.
DISP#CONN
IP address and port separated by a colon.
Read only string, set by configuration file
DISP#DEV
Device name
Description | File | Source | |||||
|---|---|---|---|---|---|---|---|
| 1 | Vaisala PTU300 User’s Guide (2019 version; device purchased in 2014) |
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| 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 | ||||
| 34 | Lantronix UDS 2100 User Guide |
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| 5 | Smaller Footprint Power Supply Datasheet |
| https://www.lantronixtri-mag.com/products/uds2100/#tab-docs-downlo |
Relevant Software
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Description
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Files
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Python 2 software written by a student some years back. These lines of code were used to read values from the Vaisala while it was installed at Keck.
That installation was using a USB interface on a Windows machine. Not sure if the current serial interface will change anything here.
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| View file | ||
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|
/wp-content/uploads/2021/05/L6R12H_Series_2021-01.pdf (Linked off the DigiKey product page) |
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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. |