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Write the following sentences in the Active Voice.

1. ET was primarily used by astronomers as the time-independent variable for planetary ephemerids.

2. Time measurements can be divided into two general categories.

3. Time interval can be measured with the most resolution and the least amount of uncertainty.

4. Quartz oscillators are used extensively in wristwatches, wall and desk clocks, and electronic circuits.

5. Few are built, and most are owned by national standards laboratories.

6. In 1984, ET was replaced by Terrestial Time.

7. They must be measured and accounted for when performing an uncertainty analysis of a timing system.

8. Groundbased systems such as LORAN-C are expected to be phased out .


11.Look at the picture which shows the STM (stop-time measurement device) and fill in the gaps with appropriate words and word combinations given below.

a) safety distance

b) stop signal

c) reciprocating (stroking or cycling) machines

d) position/velocity transducer

e) milliseconds

f) periodically check the machine's stopping time

g) meter

h) stopping time of a machine

i) hand-held actuator


The STM (stop-time measurement) device measures the time it takes a machine to stop after a signal is given. It is mainly used on , such as mechanical or hydraulic presses and press brakes.

Industry uses this type of device to find the before installing safeguarding devices such as a two-hand control or a presence-sensing device. The stopping time measured by the STM device during the hazardous portion of the cycle is used in the OSHA (Occupational Safety and Health Administration) or ANSI (American National Standards Institute) formulas to calculate the which is used to establish the location of the safeguarding device in relation to the nearest hazard. This device can also be used to to ensure that the current safety distance corresponds to the current condition of the machine's stopping ability.

The portable design makes the STM very easy to use. A programmed is provided, which releases or actuates a button or other operator-controlled device on the machine during the hazardous portion of the cycle.

When using this STM device, the display gives either the stopping time of the machine in (thousandths of a second), or the calculated safety distance in inches. The safety distance is based on the hand speed constant of 63 inches (1.6 meters) per second.

This device consists of three major components:
1. The which is the processor containing the electronics and display.
2. The which detects motion and provides the programmed output signal to stop the machine.
3. Thewhich automatically releases or pushes a button or other device on the machine. It is also used to operate the flag when presence-sensing devices are used as the safeguarding method.

Date: 2016-04-22; view: 163

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