Hello sir,
we have choosen LMP91200 for PH measurement..here is the sensor details
sensor has 3 pins and it is ISFET based sensor..The reference electrode(AG/Agcl) is inside a glass tube filled with KCL solution.They call it as gate... the other 2 connections are source and drain. it does not need temperature compensation..
it is working well with old design (Discrete IC) and produces (0.865V with ph4 solution, 1.040v with ph7, 1.175v with ph10) ..now we are planning to replace it with LMP91200. we dont need SPI ..just default setup for PH is fine..and also we dont use any connectors directly soldering this wires of sensors..
we tried already with one LMP91200, 0.1uf -- on VCC, 0.1uf -vref. vcc range tried from 2 to 5v.
scl,sdi--gnd
csb,vref--vcc
VCM---- drain of sensor
guard1,2---ref electrode
inp--source of sensor
vout single ended mode with ref to gnd..
tested with multimeter voltage
problem ---vout variation is very low...(at 3V vcc,vref, vout --(ph4--1.512V, ph7-1.520,ph10-1.532)..and also mostly repeated same values not coming..keeps on varying...so help me out.Thank u
