Xylem iRIS 150 GPRS DATALOGGERS - Manual (Page 13)

7 – IRIS 150 V1.11 User Guide
iQuest (NZ) Ltd - PO Box 15169, Hamilton, New Zealand Tel: +64 7 857-0810 Fax: +64 7 857-0811 Email: [email protected] 7
4.2.3 Analogue Inputs
Analogue inputs are uni-polar 0-5Vdc with 12bit resolution. They present a load impedance of approximately
100K
Ω
.
Suitable scaling factors should be chosen to convert from a raw value of 0-5000, which reflects the input
signal range of 0-5V (0-5000mV). When current sources are used, an internal sink resistor (250
Ω
) is
connected between the analogue input and AGND. The diagram below shows the position of the two
analogue links. Fit the link to set the analogue input to current mode, or remove the link to set it to voltage
input mode (default).
Hint: If removing a jumper, simply fit it to one pin only of the connector to avoid it being lost.
Figure 1 – Analogue Selection Jumpers
4.2.4 Digital Inputs
The two digital inputs are jumper selectable for either mechanical or electronic operation. In either case it is
necessary to pull the input down to 0Vdc to activate it. Inputs will handle up to 30Vdc in the off state for
parallel connection across existing equipment. Jumpers are positioned to the left hand side of the I/O
connector. The top jumper is for Digital Input #1 and the middle jumper is for Digital Input #2.
Fit the jumper for mechanical switching at up to 20Hz. In this mode a 100nF capacitor is fitted across the
input to provide limited hardware debounce, preventing false triggering due to contact bounce. Remove the
appropriate jumper for electronic switching at up to 5kHz.
Hint: If removing a jumper, simply fit it to one pin only of the connector to avoid it being lost.
Figure 2 – Digital Input Debounce Jumpers
DI2 Debounce
Jumper (JP2)
DI1 Debounce
Jumper (JP1)
AIN2 Jumper (JP4)
AIN1 Jumper (JP3)
IMPORTANT NOTE!
In almost all installations where an iRIS is
connected in parallel with other equipment to
share a common pulse input (e.g. from a flow
meter), there has not been a detrimental
effect, as the iRIS inputs present a relatively
high impedance to the circuit. However, in the
event that connecting an iRIS does cause
pulse failure, iQuest recommend removing the
debounce selection link for the appropriate
input. This sets the input to electronic
switching mode, even if the actual pulse
source is a clean contact (reed switch or
similar).