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Summary of Contents for Unihedron SQM-LU
- Page 1 SQM-LU Operator’s Manual c Copyright 2005 - 2017 Version: 20170728 Company information Mailing address Unihedron 4 Lawrence Avenue Grimsby, Ontario L3M 2L9 Canada Telephone (905) 945-1197 (905) 945-6770 Website unihedron.com...
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Page 3: Table Of Contents
7 Unihedron Device Manager ........ - Page 4 12.4 Confirmation ........... . Unihedron SQM-LU Operator’s Manual -...
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Page 5: List Of Figures
13 Troubleshooting ........... . . 14 Glossary . -
Page 6: List Of Tables
7.33 Sensor arrangement ..........7.34 Fig:Simulation tab . - Page 7 13.3 Cannot Find UDM software ..........13.4 Driver not found .
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Page 8: Introduction
1.1 QuickStart 1. Connect the SQM-LU meter to the computer with the supplied USB cable. Wait for any device drivers to automat- ically load (if required). You may have to visit www.FTDIchip.com to get the latest VCP drivers if they do not get installed automatically. - Page 9 1.1 QuickStart CCDAutoPilot FITS4Win2 uses the MPSAS keyword for sorting and filtering image files. Unihedron SQM-LU Operator’s Manual - 20170728...
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Page 10: Measurements
2 Measurements The SQM-LU provides readings in Magnitudes per square arcsecond, abbreviated as: mpsas, and written mathematically arcsec Mpsas is a logarithmic measurement which means that large changes in sky brightness correspond to relatively small numerical changes. A difference of 5 magnitudes is a factor of 100 times the intensity. Therefore a sky brightness 5.0 arcsec darker corresponds to a reduction in photon arrival rate of a factor of 100. -
Page 11: Getting Accurate Readings
Airglow is light produced by various phenomenon in the atmosphere which prevent the sky from being totally dark. Effects of the magnetic poles of the Earth may cause airglow to be brighter near the poles. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 12: Other Luminance Scales
The Milky Way As one goes to sites with darker surface brightnesses, the fraction of the total light received by the SQM-LU which can be attributed to the Milky Way bulge increases and so the “offset” in mpas will be larger (due to the Milky Way.) The northern view of the Milky Way contributes about 0.10 mpsas under 21.5 mpsas (moonless) skies. -
Page 13: Mpsas Vs Nelm
21 (galactic center near zenith) to 24 mag/arcsec2 (very thick clouds), or 0.1 - 1.7 NSU.[1] Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 14: Theory Of Operation
3 Theory of operation 3.1 Light measurement The SQM-LU measures the darkness of the night sky to provide readings of magnitudes per square arc second through a USB connection, and is capable of internally recording readings. A light sensor (TSL237) provides the micro-controller with a light level, and readings from the temperature sensor are used to compensate the light sensor readings through the range of operating temperatures. -
Page 15: Specifications
USB FTDI VCP driver, serial port emulator at 115200baud. Physical Size 3.6” x 2.6” x 1.1” Meter precision Each SQM-LU is factory-calibrated. The absolute precision of each meter is believed to be 10% ( 0.10 mag/arcsec ). The difference in zero-point between each calibrated meter is typically 10% ( 0.10 mag/arcsec... -
Page 16: Hardware Connections
5 Hardware connections The SQM-LU requires one connection to a USB hub or a PC for configuring the device and recovering the readings as shown in Figure 5.1. Figure 5.1: Wired connection The maximum length cable per the USB specification is 15ft (3m). USB extenders exist on the market, some work up... -
Page 17: Software Development
2. Data commands are sent to the SQM-LU, and it responds with a string of characters. 3. Close the serial port so that other programs can access the SQM-LU. Note: Only one connection can be made to the SQM-LU at a time. Therefore leaving a connection open constantly prevents other connections from being made. -
Page 18: Pascal
The UDM program contains many examples of finding the SQM devices and reading data from them. It is open source and written in Lazarus/FreePascal. The source files for UDM are available here: unihedron.com/projects/darksky/cd/udm/ . Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 19: Unihedron Device Manager
Setup and retrieve data from datalogging meters. Continuously log data from connected meters. 7.1 Getting UDM UDM is supplied on the CD that shipped with the SQM-LU. The latest version of UDM is available at the Unihedron website at this location www.unihedron.com/projects/darksky/cd/ 7.2 Installation... -
Page 20: Operation
USB device listing for your operating system. These USB devices should appear as a COMM port. Also, check the troubleshooting notes in section 13 on page 62 for possible solutions. 7.3.2 Main screen The main screen of UDM consist of the following sections: Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 21: Main Menu
The file menu is used for: opening files, finding newly attached devices, and quitting the program as shown in Figure 7.2. Figure 7.2: File menu File : Open The “File : Open” menu item is used to open up previously stored log files or calibration reports. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 22: File Open Dialog
Click on “View : Simulation” to toggle visibility of the “Simulation” tab. The Simulation tab can be used to send requests to the SQM-LU to simulate conversions of frequency and period to light meter values. See page 36 for more details. -
Page 23: View : Log
UDM and stored at the displayed “TZ database path”. This path is not changeable. The Time Zone database is taken from: http://www.twinsun.com/tz/tz-link.htm Firmware files path The firmware for the SQM-LU can be updated or reverted using UDM. These firmware files are stored at the displayed firmware files path. This path is not changeable. -
Page 24: Data Logging Header
View : DL Header shows the Data-logger header editing page. See the information at www.darksky.org/measurements for a detailed description of each field. Figure 7.7: Data logging header DL : Position can be changed by pressing the Edit button which calls up the following dialog: Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 25: Tools Menu
The “Local timezone region” and “Local timezone name” are required by UDM to calculate local times of the recorded data before storing to disk. UTC timestamps are stored in the SQM-LU. The cover offset is a text only field that indicates what offset was used on the calibration data of the SQM-LU. 7.3.5 Tools menu Tools : old log to dat The “old log to dat”... -
Page 26: Tool : Old Log To Dat
Press the “Select ...” button shown in Figure 7.10 to select the file and start the conversion process. Tools : Comm terminal The “Comm terminal” is a communication terminal window used for sending manual commands and viewing the response of the selected (from the found devices window) device. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 27: Help Menu
Help : Cmdline Info shows the commands that can be used when starting UDM from the command line. Help : Version Info shows the detailed version information for the UDM software. Help : About displays a simple screen with the version identifier. Figure 7.13: Help : About Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 28: Found Device (Single)
The default port number for the SQM-LE is 10001. See Figure 7.17. Figure 7.17: Ethernet connection details The RS232 fields are editable so you may enter your own port and baud rate. The baud rate for the SQM-LR is 115200. See Figure 7.18. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 29: Information Tab
file can be accessed later from the “File : Open” menu. 7.5 Log Continuous The “Log continuous” function allows data from the connected SQM device to be logged repetitively as shown in Figure 7.20. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 30: Log Continuously Screen
5. Press “Close” when done with the continuous logging feature. Threshold setting A threshold for recording readings can be set before starting recording. Any reading greater or equal to this threshold value will be recorded in the log file. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 31: Log Continuously Threshold
Without “Synchronized” checked, the hotkey will immediately trigger a record log, and the associated annotation text will be appended to that triggered record. GPS UDM will read the data produced from an externally connected USB or serial GPS receiver. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 32: Log Continuously Gps Tab
The location, speed, time, and status information is displayed as it is received. If the GPS is enabled before logging, then the logfile is forced to ”MOVING” platform mode, and five fields (latitude, longitude, elevation, speed, number of satellites in view) are appended to each record. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 33: Calibration Tab
3. The value is sent to the SQM, and then confirmed in the right side box (Actual values column). Note that temperatures set in to the SQM use their own resolution and may not be reflected as the same value entered. For example. 24.7 C might read back as 24.8 C. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 34: Report Interval Tab
Report threshold is measured in Magnitudes per square arcsecond (mpsas), a larger positive value is darker. 7.8 Firmware tab In a case where new firmware is supplied by Unihedron to correct bugs or add features, use this tab to select and load firmware in to the SQM-LU. -
Page 35: Configuration Tab
The “Configuration tab” shows the factory-set calibration values. Calibration is performed at the Unihedron factory. A new calibration using a calibrated light source and darkroom can be performed by following the instructions on the right side of the screen. The calibration report can be logged to a data file and also printed out from this screen. -
Page 36: Sensor Arrangement
The “Simulation” tab allows the simulation of raw light sensor values for experimentation purposes. The “Start” button initiates feeding the range of values to the internal formulas of the SQM-LU and results are displayed on this tab. Raw temperature conversions are detail in Eq: 8.1 and 8.2. The simulation will stop once all the steps are complete or when the “Stop”... -
Page 37: Simulation From File
7.10.1 Simulation from file The “From file” button sends csv data from simin.csv (in the log file directory) to the SQM-LU in simulation mode and puts the output into simout.csv. The format of the csv is shown in Table 7.2: Table 7.2: simin.csv field description... -
Page 38: Accessory Options
C humidity sensors that have been tested; HIH8120, and HYT939. The selection can be made with the drop down combo-box on this tab. Enabling this sensor allows the SQM-LU to poll the sensor once per second to gather a reading which can be requested later with the A1x command. -
Page 39: Command Line Parameters
Table 7.5: Select device command line parameters Parameter Description Do not search for devices at startup. This cuts down startup time, the user must press the Find button to find devices. Display plotter window. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 40: Commands And Responses
8 Commands and responses The SQM-LU accepts a sequence of characters as a command, then executes those commands and usually provides a response of a sequence of characters. The following details are useful when programming your own interface to send data to and receive data from the SQM-LU. -
Page 41: Response Details
8.2 Response details 8.2.1 Reading request The “Reading” request “rx” or “Rx” commands the SQM-LU to provide the current darkness value as well as all variables used to generate that result. Readings produced by this request are averaged internally by using the last 8 readings and shifting those values through an 8 cell buffer then summing and dividing by 8. -
Page 42: Unit Information
Protocol number (8 digits). This will always be the first 8 char- 00000002 acters (after the “i,” response). This value indicates the revision number of the data protocol to/from the SQM-LU. The protocol ver- sion is independent of the feature version. 11-18 Model number (8 digits). -
Page 43: Calibration Commands
0123456789 123456789 123456789 123456789 123456789 1234567 8.3.2 Light calibration command Calibration of the SQM-LU is done at the factory in a controlled light and temperature environment. Executing the Light calibration command “zcalAx” arms the light calibration mode. A calibrated light source of approximately 13.5fc is supplied to the sensor. -
Page 44: Dark Calibration Command
L = Locked; Wait for unlock before calibrating after Arm command, firmware upgrades are disabled. U = Unlocked; Calibrate immediately after Arm command, Enable firmware upgrade. Carriage return (0x0d), Line feed (0x0a). An example of the response is: zxdL 012345 Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 45: Manually Set Light Calibration Offset
The “Dark calibration time period” is the amount of time that has elapsed for the light sensor to make one cycle while in complete darkness. The meter sets a time limit of 300 seconds on this value. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 46: Manually Set Dark Calibration Temperature
Description Calibration response is being returned. Manual Set Dark Calibration temperature. Value that was set into EEPROM 019.0C 10-11 Carriage return (0x0d), Line feed (0x0a). An example of the response is: z,8,019.0C 0123456789 1 Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 47: Accessories Commands
8.4 Accessories commands Some I C accessory devices can be connected to the SQM-LU when using firmware feature version 44 and above. These devices are connected by way of retrofitted wiring inside the unit or a future back panel connector. -
Page 48: Display Accessory
C 4-digit 7-segment display made by Sparkfun (model COM-11441) can be connected. All commands (seen in table 8.15) to this accessory result in a response (seen in table 8.16). Readings that are too bright for the SQM-LU will show up as . Readings that are too dark for the meter will show up as Table 8.15: Display accessory command summary... -
Page 49: Led Accessory
8.4 Accessories commands 8.4.3 LED accessory For purposes of troubleshooting, an LED with series resistor can be connected to an internal pin of the SQM-LU. All commands (seen in table 8.17) to this accessory result in a response (seen in table 8.18). -
Page 50: Relay Accessory
8.4.4 Relay accessory A Solid State Relay (SSR) accessory may be connected to the SQM-LU for generic use or for purposes of implementing a dew-heater control. All commands (seen in table 8.19) to this accessory result in a response (seen in table 8.20). -
Page 51: Continuous Reporting Commands
= Continuous reporting disabled. C = Ideal crossover firmware code enabled. c = Ideal crossover firmware code disabled. P = Continuous reporting compression enabled. p = Continuous reporting compression disabled. Table continued on next page ... Unihedron SQM-LU Operator’s Manual - 20170728... - Page 52 Table 8.23 – continued from previous page Column Example value Description U = Continuous reporting un-averaged readings enabled. u = Continuous reporting un-averaged readings disabled. Carriage return (0x0d), Line feed (0x0a). An example response is: YrCpu 01234 Unihedron SQM-LU Operator’s Manual - 20170728...
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Page 53: Setting Interval Reporting Parameters
8.6 Setting Interval reporting parameters For firmware feature 13, the SQM-LU is capable of sending timed interval reports. Each interval report is the same as the reading request report except that the serial number (feature 14) is attached at the end so that numerous reporting SQM-LUs can be distinguished from each other. -
Page 54: Interval Setting Response
Threshold value that was set into EEPROM. 00000017.60m 39-50 Threshold value that was set into RAM. 00000017.60m 51-52 Carriage return (0x0d), Line feed (0x0a). An example response is: I,0000000360s,0000000360s,00000017.60m,00000017.60m 0123456789 123456789 123456789 123456789 123456789 12 Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 55: Simulation Commands
When using the Simulation mode of the SQM-LU, make sure that nothing else interrupts the sequence of readings such as external programs reading from the SQM-LU, or settings of Interval reporting inside the SQM-LU. To read the internal simulation values, issue the “sx” command, the response is shown in table 8.26: Table 8.26: Response of request for internal simulation values... -
Page 56: Response Of Setting Simulation Values (S...x)
Calculated period from counts. 0000000.204s, 86-92 Temperature used for calculation. 029.0C 93-94 Carriage return (0x0d), Line feed (0x0a). An example response is: S,0000094000c,0000000000f,0000000245t,r, 18.04m,0000000000Hz,0000094000c,0000000.204s, 029.0C 0123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 1234 Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 57: Installation
Source of scrylic domes: www.globalplastics.ca/domes.htm 9.1.2 Cover calibration Since the meter is not weather-proof, it must be protected in some way from the elements. The Unihedron meter housing or a plastic dome is recommended. This will reduce the incoming light (approximately 15-20%). -
Page 58: Cover Maintenance
9 Installation Figure 9.2: Example cover calibration 9.1.3 Cover maintenance Keep the covering clean of dust, water, ice, and bird droppings. Unihedron SQM-LU Operator’s Manual - 20170728... -
Page 59: Default Settings
The SQM-LU contains an FTDI USB interface module. The FTDI interface has not been altered from its default. There should be no reason to alter the FTDI chip settings. The baud rate is defined by the VCP driver side when a terminal program connects to the SQM-LU. -
Page 60: Firmware Upgrade
11 Firmware upgrade See the UDM “Firmware tab” section on page 34 for instructions on updating the firmware in the SQM-LU. 11.1 Details The SQM-LU contains a micro-controller that is equipped with a boot-loader mechanism which is enabled for a few seconds after reboot/reset. -
Page 61: Calibration
A fluorescent light or green LED is used to simulate the spectrum that the meter would see during the night sky. A light meter is used to adjust the light reading to 13.5 fc at the place of the SQM-LU. The light calibration routine inside the SQM-LU expects to see this value. -
Page 62: Reading Seem Too Bright
Microsoft Edge has protections in place to hide file lists on remote drives. Solution Use the File Manager to navigate the CD to the Windows directory then install from there. Or, get the latest Windows version of UDM from the Unihedron website: unihedron.com/projects/darksky/cd/Windows/ Table 13.4: Driver not found... -
Page 63: Recording Stops
Remove any other USB devices attached to the system to troubleshoot this problem. Try to reassign the SQM-LU to another COM port using the Windows Device Manager. For example, it the SQM-LU is assigned to COM1, then try to assign it to a free COM port number. Table 13.6: Recording stops... -
Page 64: Meter Cannot Be Found By Windows Operating System
7. Let this run for at least 1000 records and watch that are no “Records missed”. Table 13.8: Meter cannot be found by Windows operating system Problem The windows computer cannot identify the SQM-LU, and re-installing the FTDI device drivers does not help. Cause The Windows FTDI driver installation may be storing old attempts at installing drivers that should have been cleared out. -
Page 65: Cannot Get A Reading
The Serial Number is printed on the bottom of the unit. The above will identify which COM port the SQM-LU has been assigned. If the SQM-LU is plugged in, the active COM port will show up in this list: HK LOCAL MACHINE... -
Page 66: Glossary Of Terms
This type of memory has a limited write/erase cycle as well as a lifetime for data retention. In the SQM-LU, the parameters in the micro-controller can be written 1 million times and last for 100 years. - Page 67 [4] Olof Carlin, Nils. About Bradley E. Schaefer, Telescopic limiting Magnitudes, Web page discussion of brightness in Schaefer (1990) and Clark (1994). http://w1.411.telia.com/ ~ u41105032/visual/Schaefer.htm(accessed7/ 2003) [5] NELM Converter, K. Fisher fisherka@csolutions.net Rev. 8/2006 http://unihedron.com/projects/darksky/ NELM2BCalc.html [6] Moon Phase Pascal code in UDM is from the public domain library: Moon.pas Copyright 1997-2001 Andreas H¨...
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