Using the CPO timer

• All of the items below should be in the“Little Black Box of Science”

CPO Timer Inputs• It doesn’t make a difference what color (red or

blue) phone cord you use for input A or B.• However, the A cord/photogate should be the top

photogate.

CPO Computer

Photogateuses an invisible beam of infra-red

light to start and stop the timer.

The 5.0 cm car “wing” triggers the Photogate

The 5.0 cm wing start and stops the timer

The timer works like 3 internal stopwatchs

Time thru A

Time thru B

Time from A to B

No times shown

Using the CPO Timer

• Turn on the A light only, if you want to know how long it took the car to go through photogate A.

• Turn on the B light only, if you want to know how long it took the car to go through photogate B.

• Turn on the A & B lights, if you want to know how long it took the car to go from photogate A through photogate B.

Using the CPO Timer

• On interval mode, you never have to push the reset button. It automatically resets every time you send the car down.

• The timer “remembers” all 3 times when you send the car down the ramp. To retrieve the times, just push the corresponding A & B buttons.

Resolution

• The smallest interval that can be measured.

The timer has a resolution of (.0001 seconds)

That’s ten thousandth’s of a second

Interval Mode

Tenth Hundredth ThousandthTen Thousandth

Accuracy• Accuracy: how close a measurement is to the true

value.

The CPO Timer & Photogates are accurate to the + or - .0005 of a

second.

Precision: How close together repeated

measurements are.• Which group is more precise?

Group A (s)

Group B

(s)

.0238 .1487

.0296 .1482

.0201 .1479

.0193 .1485

.0333 .1483

“IFR”Index Finger Release

• This will make a big difference on the precision of our data!• Good “IFR” technique should give us a precision

of + or - .0005 seconds

Accuracy & Precision