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Version 2.1 – November 2016

5/7

3.3 Connecting Hose

Sensirion recommends a hose with an inner diameter

of 3.18 to 3.8mm (1/8 to 3/20 inch). Due to the dynamic

measurement principle, a small air flow is required

(Figure 3) which leads to a dependence on the length

of the hose (Table 4). Tubes up to 1 m show less than

2 % error of the measured value (Table 4).

Figure 3: Typical air flow through the SDP1108-R. Please note:

1 scc/min = 1 cm3/min at 0°C and 1013 mbar pressure

(1 sccm = 0.001 norm liter).

Table 4: Influence of the length of the connecting hose on

the accuracy (using 4 mm inner diameter). Deviation is

given in % of the measured value. Example SDP1108-R: a

500 Pa difference pressure is shown as 492.5 Pa when

using 1 m tube with 4 mm inner diameter.

Table 5: Maximum flow through the sensor element.

SDP1108-R

Mass flow through sensor element:

123 sccm (@ 500 Pa)

4 Electrical Specifications

4.1 Power Supply

The SDP1108-R differential pressure sensor requires a

stable voltage supply of 5.0 V. The requirements for the

electrical supply are specified in Table 6.

4.2 Voltage Output

The SDP1108-R features a voltage output from 0.25 V

to 4.0 V. An output voltage below 0.25 V indicates a

negative differential pressure (not calibrated).

The resistive load at the output pin should be larger

than 20 kOhm. The capacitive load at the output pin

must not be larger than 200 pF. If the design shows a

larger capacity at the output pin an additional resistor is

required in series at the output (e.g. 620 Ohm).

Table 6: SDP1108-R electrical characteristics.

Parameter

Conditions

Min.

Typ.

Max.

Units

4.75

5.0

5.25

VDC

Operating Current

5 V, no load, zero flow

5.1

6

mA

20

200

pF

20

100



k



Hose length

SDP1108-R

@FS

@0.5 FS

0.5 m (20 inch) -0.75%

-0.95%

1.0 m (40 inch) -1.5%

-1.9%

2.0 m (80 inch) -3.0%

-3.8%