Datasheet

Table Of Contents

OUTPUTT VOLTTAGE (1V/DIV)

TIME (25ms/DIV)

INPUT PULSE (100mV/DIV)

LMP91000 OUTPUT

TEST PULSE

LMP91000

SNAS506H –JANUARY 2011–REVISED MARCH 2013

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SENSOR TEST PROCEDURE

The LMP91000 has all the hardware and programmability features to implement some test procedures. The

purpose of the test procedure is to:

a. test proper function of the sensor (status of health)

b. test proper connection of the sensor to the LMP91000

The test procedure is very easy. The variable bias block is user programmable through the digital interface. A

step voltage can be applied by the end user to the positive input of A1. As a consequence a transient current will

start flowing into the sensor (to charge its internal capacitance) and it will be detected by the TIA. If the current

transient is not detected, either a sensor fault or a connection problem is present. The slope and the aspect of

the transient response can also be used to detect sensor aging (for example, a cell that is drying and no longer

efficiently conducts the current). After it is verified that the sensor is working properly, the LMP91000 needs to be

reset to its original configuration. It is not required to observe the full transient in order to contain the testing time.

All the needed information are included in the transient slopes (both edges). Figure 35 shows an example of the

test procedure, a Carbon Monoxide sensor is connected to the LMP91000, two pulses are then sequentially

applied to the bias voltage:

1. from 0mV to 40mV

2. from 40mV to -40mV

and finally the bias is set again at 0mV since this is the normal operation condition for this sensor.

Figure 35. Test Procedure Example

Product Folder Links: LMP91000