Measuring Instruments
Calipers
The vernier caliper and the micrometer caliper, pictured here, are instruments for making precise measurements of length.
Figure 1
Balances
The balance you will use in the laboratory is a modern, digital balance. Pressing the ON/TARE button will re-zero the machine. After the 0.0 g is seen on the readout, you may place your mass on the balance. These balances are delicate instruments and should never be overloaded. 4,000 g is the operating limit.The Smart Timer
In many of the exercises in this manual, you will be called upon to measure time intervals and frequencies (number of events occurring in a given time interval). To help you with this you will use a Smart Timer. The PASCO ME-8930 Smart Timer is an accurate, versatile digital timer and measurement system for the student laboratory. The Smart Timer offers 0.1 ms timing resolution and an easy-to-use memory function. The Smart Timer measures several types of events detected with PASCO's digital sensors, including speed and acceleration using standard photogates.Features
The Smart Timer's memory function makes it easy to time events that happen in rapid succession, such as a dynamics cart passing twice through the photogate, once before and then again after a collision. The 0.1 ms resolution is especially useful in some experiments, such as measuring velocity or acceleration during free fall. The Smart Timer can calculate velocity before and after a collision between two carts using a single timer. With the new fence design and sensing logic, parallax errors are eliminated and timing accuracy is improved considerably over existing timing options. The Smart Timer's internal microcontroller also eliminates the problem of incorrect readings due to multiple passes through the same photogate by "understanding" the type of measurement selected and ignoring multiple passes. The Smart Timer has many different options for timing and calculating values based on inputs from a variety of sensors. The graphics on the keypad aid in the selection of the appropriate timing mode. Options include one or two gates, fence, and pendulum modes. These modes allow you to measure the speed of an object as it passes through the photogate or between two photogates, or to measure the period of a pendulum. The stopwatch mode lets you use the timer as an electronic stopwatch. The Smart Timer can measure speed and acceleration for both linear and rotational motion experiments. Alternatively, the time can be measured directly, and the speed and acceleration can then be calculated by the student. The speed and acceleration measurement features can be enabled or disabled using a switch inside the Smart Timer.Use With Photogates
The Smart Timer is optimized for use with PASCO's ME-9204B Accessory Photogate (available separately). These narrow-beam infrared photogates plug directly into the Smart Timer and are used to provide the timing signals. An LED in one arm of the photogate emits a narrow infrared beam. As long as the beam strikes the detector in the opposite arm of the photogate, the signal to the timer indicates that the beam is unblocked. When an object blocks the beam so it doesn't strike the detector, the signal to the timer changes. In one gate mode, a single photogate lets you measure the time, velocity, or acceleration of a fence as it passes through the photogate. Two photogates are used for collision experiments using one or two carts or for experiments where the velocity of a cart must be measured at two different points. In two gate mode, two photogates are used and the time to travel between the two can be measured. This mode can also be used to measure time of flight using the ME-6810 Time-of-Flight Accessory.
Figure 2
Quick Cross-Reference for Suggested Activities and Smart Timer Modes
Figure 3: Image credit: PASCO