User manual TEXAS INSTRUMENTS CBL 2 SYSTEM GETTING STARTED

[. . . ] Radio Shack is a trademark of Technology Properties, Inc. Safety Instructions Observe all warnings, cautions, and other safety instructions indicated on the product and in the documentation. These instructions are intended to reduce the risk of injury, possible electrical shock, or damage to the unit. Connecting 115/230 Volts AC to any input probe may cause serious injury or electrical shock, and may damage the unit. Low-Voltage Unit WARNING!Personal injury and damage to the unit may occur if voltages exceed 30 Volts DC on CH1, CH2, or CH3; or if voltages exceed 5. 5 Volts DC on SONIC, DIG IN, or DIG OUT. [. . . ] Theoretically the relationship between light intensity and distance is given by a function of the form I= A d2 where I is the intensity of the light and d is the distance from the tip of the light probe to the light bulb. If this is correct, what would you expect the ratio to be between the light intensity measurements made at . 5 meter and 1 meter? What would you expect the ratio to be between the light intensity measurements made at 1 meter and 2 meters? What would you expect the ratio to be between the light intensity measurements made at 1. 5 meters and 3 meters? 4. Compare the ratios from the actual data to your predictions above. 2000, 2003 TEXAS INSTRUMENTS INCORPORATED GETTING STARTED WITH THE CBL 2?There is probably some difference between the predictions and the actual data. This frequently happens. One possible source of experimental error is in measuring the distance from the tip of the light probe to the light bulb. Make several different measurements trying to place the tip of the light probe exactly 1 meter from the light bulb. There are a number of things you can do to try to minimize this source of error. Describe some possibilities. 8. You can investigate the effects of errors in measuring the distance from the tip of the light probe to the light bulb by deliberately making errors. What is the effect of an error of 5 cm when the distance is supposed to be . 5 meter? 9. What is the effect of an error of 5 cm when the distance is supposed to be 1 meter? 10. You can investigate the effects of this source of error by deliberately introducing an extra light and comparing measurements made with this extra light on and with this extra light off. How can you correct for extra light in the room? Repeat the original experiment doing everything you can to minimize measurement error. 46 GETTING STARTED WITH THE CBL 2?SYSTEM 2000, 2003 TEXAS INSTRUMENTS INCORPORATED Teacher Section Theory The relationship between light intensity and distance can be described by a function of the form I= A d2 but there are so many potential sources of error that students are likely to see discrepancies between theoretical predictions and the data. It is also very important for students to realize that not all such discrepancies can be dismissed as ?experimental error. ?This activity addresses this objective by attempting to identify and compensate for experimental error. that is, with no light the light probe may not read zero. One way to convey the idea that not all discrepancies can be dismissed as ?experimental error?is by having students make light intensity readings using a fluorescent bulb. Because fluorescent bulbs flicker, these measurements jump around. Answers Sample data with sample answers: 1. (Intensity falls off rapidly as distance increases. ) 2. Distance . 5 1 1. 5 2 2. 5 3 3. 5 Light Intensity . 228 . 070 . 034 . 026 . 020 . 014 . 013 2000, 2003 TEXAS INSTRUMENTS INCORPORATED GETTING STARTED WITH THE CBL 2?The measurement made at . 5 meter should be 4 times the measurement made at 1 meter. The measurement made at 1 meter should be 4 times the measurement made at 2 meters. The measurement made at 1. 5 meters should be 4 times the measurement made at 3 meters. 4. [. . . ] SYSTEM B-7 Command 7 Request System Status {7} Current software version If non-zero, CBL 2?should be reset Results Battery is OK for use Battery is low during sampling Battery is low all the time Generates and prepares to return the following status information. softwareID error battery 0 1 2 8888 sample time trigger condition channel function channel post channel filter num samples Constant value; ensures the status message was received correctly Sample time commanded by host during last sample run Triggering condition commanded by host during last sample run Triggering channel commanded by host during last sample run Post-processing setting commanded by host during last sample run Filter commanded by host during last sample run Number of samples commanded by host during last sample run (or, if sampling was aborted, the actual number of samples taken) Results No time was recorded in the last run Absolute time was recorded in the last run Relative time was recorded in the last run record time 0 1 2 temperature Temperature used for temperature correction of sonic data during last run (if a sonic sensor was selected) Results No sound commanded Sound is enabled piezo flag 0 1 B-8 GETTING STARTED WITH THE CBL 2?SYSTEM 2000, 2003 TEXAS INSTRUMENTS INCORPORATED system state 1 2 3 4 5 99 Idle Armed Busy Done Self-test Initializing code data start First point of data available for transmission to host unless host has sent Command 5 to override Last point of data available for transmission to host unless host has sent Command 5 to override System ID that was set using Command 6 data end systemID Command 8 Request Channel Status {8, channel, request type} Returns a list with three elements: E 1, E 2, E 3 channel=1, 2, 3, or 11 E 1 = sensor type (one of the operation options shown under Command 1) E 2 = last valid data read from sensor, if any [only valid when sampling is active] (not applicable to CH1 ops 5, 6, 7 or CH21 or CH31) E 3 = last valid data position (data buffer location number where that data is deposited) [only valid when sampling is active] request type=0 or 1 0 = returns current data (such as, read and return channel ID information) 1 = returns data stored when channel was last set up Command 9 Request Channel Data {9, channel, mode} Immediately reads and returns one data point. 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