Utility Screens - • Using the Xplorer GLX Standalone

This chapter describes the Output screen, Calculator, Notes screen, and Stopwatch.

O u t p u t

The Output screen is the control panel for generating sound through the GLX’s built-in speaker or through headphones or amplified stereo speakers connected to the signal output port.

To Open the Output Screen

From the Home Screen do one of the following:

use the arrow keys to highlight the Output icon, then press ; or click the Output icon.

Navigating in the Output Screen

The Output screen is divided into three parts: Output Settings, Left Output Chan-nel, and Right Output Channel. There are three controls within each part, for a total of nine controls. One of the controls is always highlighted. Use the arrow keys to move the highlight. Press to select the highlighted control. If a menu opens, use the up and down arrow keys to highlight the desired setting and press . If a cursor appears, type the desired value and press . The Volume, Fre-quency, and Phase controls can also be set using and .

If you are using a mouse, click the control that you would like to set; then click the desired menu option, or type the desired value.

Output Function Keys

F1 and F3 On/Off

Press to turn the left channel on or off, press to turn the right channel on or off.

F2 and F4

When the Frequency control for the left or right channel is highlighted, press or to set the step size for that channel. From the menu that opens, select one of the step sizes or select Custom Step to enter any value. The step size determines the amount by which the frequency changes when you press ,

, , or (see “Frequency” below).

The Output icon on the Home Screen

Output Settings

OutputLeft Channel

Right Output Channel

F3 F4 F1 F2

Output function keys

F1 F3

F2 F4

Output Settings

¹ Output Device

Highlight the Output control and press to select the output device that you are using.

Headphones Select this option to play sound through headphones connected to the signal output port on the left side of the GLX.

Internal Speaker If there is nothing connected to the signal output port, select Internal Speaker to play sound through the GLX’s built-in speaker.

External Speaker Select this option to play sound through a pair of amplified stereo speakers connected to the signal output port.

Power Amplifier Selecting this option puts the Output screen into a special mode for the optional GLX Power Amplifier.

Volume

The Volume setting determines the overall loudness of the output sound. High-light the Volume control and press or to change it incrementally; or press to select the desired volume from a menu.

Speaker Config

When Output Device is set to Headphones or External Speaker, the two options for Speaker Config are Stereo and Mono. When Output device is set to Internal Speaker, Mono is the only option. In Mono configuration, the signals from both channels are combined within the GLX; both external speakers or both sides of the headphones play the same combined signal. In Stereo configuration, the Left Output Channel plays through the left speaker or the left side of the headphones, and the Right Output Channel plays through the right speaker or the right side of the headphones.²

Left and Right Output Channels

Wave

Highlight the left or right Wave control and press to set the wave form of each output channel. The options are Sine, Square, Ramp, and Triangle.

Frequency

Highlight the left or right Frequency control and press or to change the frequency up or down by the value specified above or ; press or

to multiply or divide the frequency by that value. To enter the frequency directly, press . The frequency can be set between 240 and 5000 Hz for the internal speaker, or between 60 and 5000 Hz for external speakers and head-phones.

Phase

Highlight the left or right Phase control and use or to adjust the phase up or down, or press and enter the desired phase. The phase of each channel can be set between -360° and 360°.

1The output settings in the Output screen can also be changed in the Audio Settings dialog box, accessed from the Settings screen (see page 87).

When you change the settings in one location, they are automatically updated in the other location.

2If you are using stereo headphones to demonstrate beats or destructive inter-ference, set Speaker Config to Mono so that each ear can hear both tones.

Sine

C a l c u l a t o r

You can use the GLX Calculator like a regular calculator for finding the result of a simple expression, like a graphing calculator for plotting equations, and for per-forming operations, in real time, on streams of data collected from sensors and on sets of manually entered data.

To Open the Calculator

From the Home Screen, do one of the following:

press , the function key below the Calculator icon;

use the arrow keys to highlight the Calculator icon, then press ; or click the Calculator icon.

From anywhere in the GLX environment, you can always get to the Calculator with the shortcut + .

Types of Calculations

The Calculator supports four types of calculations: basic, algebraic, graphing, and sensor-based. The following examples will demonstrate the four types.

Basic Calculations

Basic calculations involve only numerals (no constants or variables). Open the Calculator and try this:

• On the first blank line, type:

1 + 1

The Calculator responds by adding an equal sign and the result. It also dis-plays the result at the bottom of the screen. Notice that the cursor has moved to the next line.

• On the next line type:

9 * (8 + 3)

To type the multiplication symbol (the asterisk), press .

For the parentheses, press once to open the first Functions menu³; use the arrows to highlight the pair of parentheses, then press .

Note that has the same effect as .

The Calculator icon on the Home Screen

Cursor moves to next line

Result is added to the entered expression

Result also indicated here

X F1

Pair of parentheses F1

First Functions menu

3For more information on the Functions menus, see page 48.

• Press the up arrow key to put the cursor back on the above expression and modify it to read:

9 * (9 + 3)

When you type something into the middle of an existing expression, the new characters are inserted without overwriting anything; press to delete the characters that you don’t want.

Note that the correct result does not appear until you have moved the cursor to a different line by pressing or , or the up or down arrow key.

Algebraic Calculations

Algebraic calculations involve symbols (letters or words) standing for constants.

When you enter an algebraic expression, the GLX fills in the result if it knows the value of every symbol used in the expression. If it does not know the value of a symbol, it will prompt you to enter it.

If you are entering an equation to be graphed, leave one symbol undefined.

See “Graphing Equations” on page 44 for more information.

Try these examples:

• Type:

a + 3

For the a symbol, press twice to open the second Functions menu. Use the arrow keys to highlight

a

, then press .

For more information on the Functions menus, see page 48.

The Calculator does not know the value of a, so it prompts you with:

a =

Type:

5

The Calculator fills in the result of the original expression.

• Try entering a new value for a on the next line:⁴

a = 6

Note that the original expression still reads

a + 3 = 8

This expression has just been modified, but the user has not yet pressed or so it appears to

show an incorrect result.

= Õ

F1 F1 press twice

Second Functions menu

The Calculator fills in the result of a+3 when the value of a is entered.

4For the a symbol, press twice and select it from the second Functions menu.

When there is more than one definition for the same symbol, the calculator uses the first definition. To avoid confusion, do not define a symbol more than once. If you want to change the value of a symbol, use the arrow keys to go back to the original definition and change it.

• When you are prompted for the value of a symbol, you can enter another expression rather than a simple number. Type:⁵

b + 3

When prompted for the value of b, enter:

1 + 1

The Calculator displays the value of b at the bottom of the screen and fills in the result of b + 3 on the line above.

• Rather than a simple expression, you can enter a complete equation for the Calculator to evaluate. Enter:⁶

z = y * 2

When prompted for the value of y, enter:

4

The Calculator indicates the value of y at the bottom of the screen. To see the value of z at the bottom of the screen, use the up arrow key to put the cursor on the definition of z.

Reposition the cursor to see the value of z Do not

do this

5For the b symbol, press twice and select it from the second Functions menu.

Calculator fills in result

Value of b

6For the z or y symbol, press twice and select it from the second Functions menu.

Value of y Cursor

Value of z Cursor

• A symbol does not have to be a single letter. The Calculator will recognize any text string (without spaces) as a symbol, including text strings that con-tain numerals. (To type text on the keypad, see “Num Lock” on page 50.)

Graphing Equations

If you enter an equation that contains one undefined variable to the right of the equal sign, the GLX can graph it.

• Type:⁷

y = m * x + b

• When prompted, assign numeric values for m and b, but not for x.

• Press the up arrow key to place the cursor on

y = m

x + b

and press . The equation is plotted in a preview graph in the lower half of the screen.

The preview graph will always show the equation that the cursor is on.

(Move the cursor down to m and see what happens.)

Press again to turn off the preview graph.

• The preview graph is a simplified version of the Graph screen, without all of the scaling and analysis features.⁸ For the normal full-screen Graph, press

+ , then select the calculation ( ) from the data source menu of the vertical axis.

Examples of text strings used as symbols in algebraic calculations

7For the y, m, x, or b symbol, press twice and select it from the sec-ond Functions menu.

x is undefined

Enter values for m and b, but not x

Cursor

The preview graph shows the equation that the cursor is on

8If you are using a mouse, you can scale the preview graph by direct manipulation (see page 17).

See “Data Source” on page 15 for more information about selecting data in the Graph.

• You don’t have to use x as the undefined variable; whichever symbol you leave undefined on the right side of the equation will be plotted on the hori-zontal axis. However, the label on the horihori-zontal axis will always read “x,”

even if the variable used in the calculation is not x.

Do not leave more than one symbol on the right side of the equation unde-fined. If you do, the graph will use both of them as model ranges with confus-ing results.

• The text on the left side of the equation does not have to be y. The text to the left of the equal sign is the name of that calculation, and will appear as the vertical axis label on the Graph. It can consist of any combination of letters, numerals, and spaces.

If you are defining more than one equation to be graphed, use different text on the left side of each equation so that you can distinguish between them in the data source menu of the Graph.

Sensor-based Calculations

You can create a calculation to automatically transform any data collected by a sensor.

• Connect a temperature probe to one of the ports on the left side of the GLX.

Press to collect data for a few seconds. Press again to stop.

In the Graph, select the calculation from the data source menu

Each equation can be identified in the data source menu of the Graph by its unique name

When defining multiple equations to be graphed, give each a unique name

• Open the calculator. On the first blank line, enter:⁹

d = [Temperature (

^°

C)] - 20

Instead of typing “[Temperature (°C)]”, select it from the [Data] menu.¹⁰

Open the [Data] menu; select Temperature and °C

• Press the up arrow key to place the cursor on the calculation. Press to view the calculation on the preview graph. Note how the calculated data dif-fers from the original temperature data.

• Press + to open the full-screen Graph. Press twice to open the vertical data source menu and choose the calculation (see right).

See “Data Source” on page 15 for more information about selecting data in the Graph.

• Press to begin collecting data again. Note that the calculation is per-formed in real time on the new data.

• Calculations have no units by default. To assign units to a calculation, select Data Properties from the data source menu in the Graph (see “Data Proper-ties” on page 69).

• In addition to sensor-collected data, calculations can operate on other data sources, such as manually entered data sets, other calculations, and time. To insert any data source into a calculation, press and select it from the [Data] menu.

Uses of Sensor-based Calculations

Shift Data Vertically In the example above, the sensor-based calculation sub-tracts 20 °C from the measured temperature. This calculation might be used in an experiment where the difference between the measured temperature and room temperature is of interest (a study of Newton’s law of cooling, for instance). The calculation in the example shifts the temperature graph down by 20 °C.

Time-shift Data When a data plot appears on the Graph with Time on the hori-zontal axis, the plot can be shifted right or left with a time-based calculation.

For example, the graph shown at the right is from an experiment in which a tem-perature probe was dipped into warm water, then removed, wiped dry, and allowed to cool. The relevant data start after the probe was dried, about 14 sec-onds from the start of data collection. To make the analysis simpler, the graph needs to be shifted left so that the relevant data start at time zero. To do so, create the calculation below. (To insert [Time (s)], press and select it from the [Data] menu.)

[Time (s)] - 14

9For the d symbol, press twice and select it from the second Functions menu.

10To select Temperature from the [Data] menu

Keypad

1. Press to open the [Data] menu.

2. Use the up or down arrow key to high-light Temperature and press ; or press the number on the keypad cor-responding to Temperature.

3. The units menu will open. Use the up or down arrow key to highlight °C and press ; or press the number on the keypad corresponding to °C.

Mouse

1. Click [Data] to open the menu.

2. Click Temperature.

3. The units menu will open. Click °C.

Calculation

In the Graph, choose the calculation from the data source menu

This data plot needs to be time-shifted

Plot the calculation on the horizontal axis in place of Time to create the graph shown below. (See page 28 for instructions on selecting data for the horizontal axis.)

Convert Units of Measure Most of the sensors used with the GLX are pro-grammed with SI units (or the International System of Units) and, in some cases, other common units. If you wish to make a measurement using units that are not programmed into the sensor, create a calculation to convert the measured data.¹¹ For example, if you are using a Motion Sensor, which measures position in meters, and you want to convert the measurement to centimeters, create the cal-culation below. (To enter text, see “Num Lock” on page 50.)

position in cm = [Position(m)]*100

Calculate an Experimental Value In some experiments, it is possible to cal-culate an experimental value based on a sensor measurement. For example, in an experiment where a Motion Sensor measures the acceleration of an object, you can use the Calculator to calculate the net force:

force = mass * [Acceleration (m/s/s)]

The Calculator will prompt you for the value of mass.

Compare Measurements from Two Sensors When collecting data with two sensors, a calculation can be used to compare the separate measurements.

For example, if you are using two temperature probes, named “Temperature” and

“Temperature2,” and you want to know the temperature difference between them, create the calculation:

[Temperature (

^°

C)] - [Temperature2 (

^°

C)]

Graph Linearization In some cases, such as the examples below, you may want to linearize data so that you can use the Linear Fit tool in the Graph display (see “Linear Fit” on page 19). To do so, use the Calculator to calculate the square, square root, natural log, etc., of the measured data. (See “F1 Functions” on page 48 for more information on these and other functions.)

• The graph to the right shows period (T) versus length (L) data from a simple pendulum. The graph can be linearized by plotting T² versus L. The slope of the graph (shown below on the left) is 4π²/g, where g is the free-fall acceler-ation. Alternatively, the graph can be linearized by plotting T versus . On the graph (shown below right), the slope is .

This data plot has been time-shifted by -14 s

11For certain measurements (tempera-ture, for instance), it is not necessary to calculate a units conversion because the sensor is programmed with other com-mon units of measure (°C, °F, and K), which can be selected from the units field of any display. See pages 15 and 29.

Period vs. Length for a simple pendulum

L 2π⁄ g

T vs. √⎯L for a simple pendulum T² vs. L for a simple pendulum

• The position versus time graph of an object in free fall (below right) exhibits a typical quadratic relationship. The object was dropped from a height of 0.79 m, with the release occurring 2.2 s after the start of data collection. The graph can be linearized (as shown below right) by replacing Time on the hor-izontal axis with the calculation (

[Time (s)]

^-2.2)

^2

. The slope of the best-fit line is , where a is the acceleration of the object.

• Voltage versus time graph for a discharging capacitor is shown below on the left. The graph the natural log of voltage versus time is a linear (below right).

The slope of the line is , where C is the capacitance and R is the resistance through which the capacitor discharges.

Calculator Function Keys

F1 Functions

Press (or click Functions) repeatedly to access the three Functions menus.

These menus contain the following items.

• Functions: sin, cos, tan, arcsin, arccos, arctan, ^2, log, ln, sqrt, 10^, e^

• Operators: ^ (the exponent operator)

• Constants: π

• Commonly used symbols: x, y, z, m, a, b, c, d, α, ω λ, θ

• Sample expressions: y = 2x +3, y = x^2, y = sin(x), y = e^x sin(x)

• Parentheses: a pair of parentheses and a single right parenthesis

• Special Functions: limit, mod, abs, random

• Output-control Functions: outstate, outswitch, outfreq, outvolume

• Logic Operators and Functions: <, >, inrange, and, or, not a 2⁄

Linearized free-fall data Position vs. Time of an object in

free fall

1 RC⁄ –

Linearized data for a discharging capacitor

Voltage versus Time data for a capacitor

The first and second Functions menus

Special functions, output-control functions, and logic operators and functions are typically used to control the GLX’s digital and audio output. See “Output-control Calculations” on page 50 for detailed explanations of these functions and operators.

Inserting a Function When you select an item from one of the Functions menus, it is inserted at the cursor location.¹² If the item includes a pair of paren-theses, the cursor will be positioned between them.

Degrees/Radians A calculation containing a trigonometric function can be set to operate in degrees or radians. This setting is applied to each calculation sepa-rately. The lower right corner of the Calculator indicates whether the calculation

在文檔中 • Using the Xplorer GLX Standalone (頁 45-61)