Other Parts Discussed in Thread: TIDA-00561
Tool/software:
Hello,
I have been studying the reference design for LMP91200 (TIDA-00561), with particular attention to the GUARD and VCM nets. It appears, from inspecting the gerber files, that the reference design has been made compatible with some kind of triaxial SMA connector, where the centre conductor is the pH reference electrode, the GUARD nets are the inner sheath, and the VCM net drives the outer sheath. The BoM however simply references a standard SMA connector (coaxial), with outer conductor driven by VCM. Is there a suggested compatible triaxial SMA connector that would work with this reference design?
It seems that many pH probes that are available with in-built RTDs (PT100/PT1000) come with cable assemblies like this:
The cables tend to have an inner coaxial cable, with centre connected to pH solution electrode and outer connected to reference electrode. Presumably these are to be connected using INP and VCM on the LMP91200 respectively. The inner coax, PT1000 conductors, and spare unconnected conductors are then all encased in another outer layer of shielding (green/yellow in this case).
Can this type of cable support the triaxial guard configuration? My assumption is that it cannot. The inner coax must be connected to INP and VCM, meaning that the GUARD net could only connect to the out shield (green/yellow), but this is the wrong place for it. The guard should encompass the pH electrode conductor (INP) only.
Have I interpreted this correcly?
Many thanks in advance for any help.
