A command, including the measurement type and integration time, sent by the microprocessor to the 2-wire interface, sets the epc600-chip

configuration and triggers the measurement. The device operates standalone to perform the distance measurement. When it is finished,

the chip responds by sending the results: the distance value. It is without any calibration, correction or offset compensation. Based on this

data, the microprocessor computes the final measurement result in regards to the necessary correction factors e.g. quality, offset, ambient-

light and temperature drift. The actual result must be read first before starting the next capture cycle. The detailed method of communica -

tion and the instruction set are described in chapter 3.: Instruction Set. For more details refer also the the epc600 Handbook.

The epc600 range-finder uses the time-of-flight principle. It is implemented with a repeating, continuous-mode modulation signal during the

measurement phase (refer to Figure 14). Consequently, only signals returning within the maximum time slots can be detected unambigu-

ously. This corresponds for the epc600 to a maximum operating range of 15m. Strongly reflected signals outside of this range may there -

fore interfere with the measurement.

1.3.2. System sensitivity, integration time and operating range

The operational range of the complete system is limited by the sensitivity of the receiver as well as by the illumination power emitted by the

modulating light source (e.g. LED).

Time

(peak-to-peak)

Light

Intensity

Figure 14: The light detected by the receiver

relates to the integration time: The longer the integration time, the more sensitive the measurement.

measurement result) in the following way:

t

INT-REF-AC

t

INT-AC

e.g.

E

nW

/ cm

2

LSB

⋅

103

μ s

205

μ s

⋅1'000 LSB = 16 μ W/cm

2

Illumination power, remission of the object (reflectivity), sensitivity of the sensor together with the integration time are limiting the distance

operational range. For more detailed information, refer to epc's application note: AN02 Reflected power calculation.

It will probably not be possible to cover the full operational range within one integration time step due to the dynamic range of the re-

ceiver's electronics. The possibilities to extend the operating range or to influence the response time are:

■ to adapt the integration time correspondingly to the necessary sensitivity as demonstrated in Figure 15.

■ or alternatively: use an additional, external LED driver to adjust the illumination to the needed system sensitivity level (refer to

chapter 1.3.9.: Extended operating range).

The easiest way is to adapt the integration time to the current illumination situation (e.g. in Figure 15). With the command formats, which

allow adjusting of the integration time, it is easy to do. It is simple to change the integration time on the fly: a capture is initiated by a com -

mand sent to the chip.

© 2014 ESPROS Photonics Corporation

Characteristics subject to change without notice

11 / 30

Datasheet epc600 - V1.3

www.espros.ch