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**Introduction **

ETS , Electronic Total Station, is a high tech measuring instrument. It is a surveying and mapping instrument system integrated with measurements of horizontal angle、Vertical angle、distance and height difference. It is called ETS because it can complete all the measurement work on the station by placing the instrument at one time.

It is widely used in the field of precision engineering measurement or deformation monitoring, such as large buildings on the ground and underground tunnel construction.

**Specification**

Non-prism ETS range from 300 to 600 meters.

**PICTURE**

**Brief introduction of principle **

The total station can not only measure the horizontal angle and vertical angle of the target position, but also measure the distance of the target position.

The principle of distance measurement is phase measurement.

The frequency of radio band is used to modulate the amplitude of laser beam in phase laser ranging. The phase delay of one-round-trip modulated light is measured, and then the distance represented by the phase delay is converted according to the wavelength of modulated light. It’s an indirect method to determine the time required for the light to travel back and forth through the measuring line.

The specific formula is as follows:

The angular frequency of the modulated light is set asω, the phase delay generated by one round trip on the distance D to be measured is set as φ.

Corresponding time is set as t.

t=φ/ω. (1)

D=(1/2 )*c*t (2)

Substituting (1) into (2) leads to:

D=1/2 ct=1/2 c?φ/ω

ω=2πf

Obtain:

D=c/(4πf) (Nπ+Δφ)= =c/4f (N+ΔN)

φ——The total phase delay generated by the signal one-round-trip

ω——Angular frequency of modulated signal, ω=2πf

U——Unit of length, equal to 1/4 modulated wavelength

N——the number of modulated half wavelengths contained in the line

Δφ——the part less than π generated from the phase delay of the signal travel one around in the line

ΔN——the fractional part of the modulated wave contained in the line less than half wavelength

ΔN=φ/ω

The frequency c/(4πf) is a constant under given modulation and standard atmospheric conditions. At this time, the distance measurement becomes the measurement of the number of half wavelength and the fraction of less than half wavelength contained in the line, namely, N or φ.

**Recommended model**

Emitter (LD, LED)

The following bands are commonly selected: 690nm, 785nm

>690nm Recommended：HL-6738mg ( 功率30mw)

>785nm Recommended：ADL-78101TL ( 功率10mw)

>850nm LED Metal package(e.g.FM228)

**Receiver (APD)**

AD500-8TO52S2

AD500-8TO52S1 (general pigtail coupling)

Room 801,No.2,Lane 251,SongHuaJiang Road,Shanghai P.R.C

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