Advanced Photogate Set Up

Logger Pro contains many experiment files that work for most photogate experiments. It is easiest to use these files rather than set up an experiment from scratch. However, if the available experiment files do not fit the experiment you want to conduct, you can create your own experiment file.

Getting Started with Photogates

  1. Connect your Photogate(s) to the DIG or DIG/SONIC ports on the interface. If your Photogates do not auto-ID, they must be set up manually.
  2. Once the Photogate is identified, the gate status will be displayed in the data table. Block the Photogate with your hand; the status should be Blocked. Once you remove your hand, it should change to Unblocked. The status of the gate is also displayed under the toolbar.
  3. The default mode is Motion Timing. This mode is appropriate for a picket fence experiment, a pulley, or for a string of four or more daisy-chained photogates. Note: Only auto-ID photogates may be daisy-chained.

Photogate Settings

After setting up your Photogates, you can make changes to the setup by choosing Set Up Sensors from the Experiment menu. Click the Photogate in the appropriate channel box in the Sensor Setup dialog to change the settings. See below for information about the available set up options.

Set Distance or Length

(only available with Motion Timing, Pulse, or Gate mode)

Current Calibrations

Motion Timing

The Motion Timing mode uses a Photogate or pulley connected to the digital input. During operation, times are recorded as leading opaque edges of a "picket fence," bar tape, or a pulley spoke pass through the Photogate beam. These times are displayed in a data table. More importantly, if you enter the distance between the leading edges of the opaque bands in the Length of Object field, the program can analyze the times, and calculate velocities, displacements, and accelerations.

When a picket fence or bar tape is used, the width of each of the bands (b in the figure) should be at least 0.5 cm, The distance between the leading edges (d in the figure) should be at least 3 cm or larger if the picket fence is to be moving rapidly (for example in the free fall experiment). A closer spacing can be used if the object will be moving slowly; for example, on an air track glider. Motion timing uses the block to block timing interval for most calculations.

Pulse Timing

In this mode, a measurement from when a Photogate gets blocked to when it gets blocked again will be recorded.

Gate Timing

For this mode, timing will begin when the photogate is first blocked. The timing will continue until the gate is unblocked. The duration of the interruption is thus timed. If the length of the object is entered in the Length of Object field, the velocity is calculated.

Pendulum Timing

The Pendulum Timing mode uses a Photogate attached to an interface. The timing will begin when the Photogate is first interrupted. The timing will continue until the Photogate is interrupted twice more, so that you get the time for a complete swing of a pendulum or other oscillating object.

Photogate Timing

In Photogate Timing mode, only a time and Gate State column are displayed. You may add any other calculated columns as desired.

Calculated Columns for the Photogate

Logger Pro contains functions you can use to create calculated columns based on photogate data.

  1. Choose New Calculated Column from the Data menu.
  2. Enter a Name and Short Name.
  3. Click the Functions > button. Select Photogate, the select the function you want to use. See below for a detailed explanation of each of the available function.
  4. Click the Variables (Columns) > button and choose the variable to be inserted in the equation. The variable "GateState" refers to the blocked/unblocked status of the Photogate.
  5. Click Done when you have completed entering the equation.

Photogate Functions

Blocked Mid Times

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Calculate the average times between blocked events from Gate 1 to Gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Blocked To Blocked

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Returns a column of the times between successive blocked events in gate 1 and blocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Blocked To Unblocked

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Returns a column of the times between successive blocked events in gate 1 and unblocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Blocked To Unblocked Midtimes

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Calculate the average time between successive blocked events in gate 1 and unblocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Unblocked to Blocked

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Returns a column of the times between successive unblocked events in gate 1 and blocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Unblocked To Unblocked

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Returns a column of the times between successive unblocked events in gate 1 and unblocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Unblocked To Blocked Midtimes

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Calculate the average time between successive unblocked events in gate 1 and blocked events in gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Unblocked Midtimes

("Time", "GateState1", "GateState2")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
"GateState2": Optional. A column of photogate states (1's and 0's)
Calculate the average times between blocked events from Gate 1 to Gate 2. If you don't enter a "Time" column, the program will find one. If you don't enter "GateState2", "GateState1" will be used.
Pendulum Period

("Time", "GateState1")
"Time": Optional. A column of real numbers (the times of events)
"GateState1": A column of photogate states (1's and 0's)
Calculate the time between every other blocked event on Gate 1. If you don't enter a "Time" column, the program will find one.
Derivative Time Shift

DerivativeTimeShift ("Y", "X"): returns the derivative of "Y" with respect to "X". This function is specifically designed to be used with photogate and picket fence data. The derivatives returned are adjusted to estimate values at the start of the timing interval, instead of the midpoint. For details see The Physics Teacher, Vol 35, April 1997, p. 220. The article written by William Leonard is entitled "The Dangers of Automated Data Analysis." Average velocity during the time interval is equal to the instantaneous velocity at midpoint of the time interval.

Where

Second Derivative Time Shift

Numerical time-shifted second derivative("Y", "X")
"Y": A column of real numbers
"X": Optional. A column of real numbers
Numerical time-shifted second derivative. Calculates the second numerical derivative of "Y" with respect to "X". The values are shifted so that the derivatives are calculated at the midpoints between each two values. If you don't supply an "X" column, the program will find one.

Count Events Over Time X

("Time", "GateState", Interval)
"Time": A column of real numbers (the times of events)
"GateState": A column of photogate states (1's and 0's)
Interval: The time interval over which to count blocked events
Returns a column of the time intervals used in CountEventsOverTimeY.
Count Events Over Time Y

("Time", "GateState", Interval)
"Time": A column of real numbers (the times of events)
"GateState": A column of photogate states (1's and 0's)
Interval: The time interval over which to count blocked events
Counts the number of blocked events (1's) over each specified time interval. Use this function to do "Radiation Counting" with a photogate. Use with CountEventsOverTimeX to get a graphable pair of columns.