Question: PSN ADC24 Input Resistor Configuration

[John L. Males]

Larry,

Can you advise what the following input resistor configuration
represents:

R1/26/19/15 5.6k div1
R2/25/20/6 5.6k div2
R9/21/14/16 6.8k bias
R5/27/20/3 6.8k dmp-r

All with dmp-r to bias terminal input side hole and not into dmp-r
hole near bias.

My sense is these resistors are common to be customized when PSN
ADC24 boards were ordered or by user.


John L. Males
Toronto, Ontario
Canada

2026-07-23 18:16+0000 UTC eMail Start
2026-07-23 18:33+0000 UTC
2026-07-23 14:33-0400 EDT

*****Not GPG/PG Signed*****

[Larry Cochrane]

John,

Using the Input Range +-10V Ground Referenced schematic/image on this page https://www.seismicnet.com/psnadc24/ as
reference. For a +-10V input range R15 and R6 should be 47K, not 35.2k, and, R3 and R16 should be 6.8K not 2.2k. To get
an input range of +-10V you need to set the gain of the ADC's PGA to 8.

-Larry

[John L. Males]

Larry,

Thanks for your reply.

I forgot to mention the initial questions and these questions (all
of and related to) are for V1.5 of PSN ADC24 board.

I asked about the noted resistor configuration to understand if a
configuration you may have been asked to do. If so or not if you
have guess what may of been intended use, i.e. geophones?

For +-10V I know some used voltage divider resistors 35.2K/2.2K
with PGA of 2. This appears to have been the initial suggestion.
What are pros/cons of this initial voltage divider suggestion with
PGA of 2 vs 47K/6.8K with PGA of 8? Clearly you have reasons for
voltage divider that uses PGA of 8 instead of 2.

I often observe where the damping resister is not connected at PCB
TH connector closest to bias resistor to damping resistor PCB TH,
but connected to bias resistor PCB TH nearest input terminals no
matter if input bias resistor is populated or not. What might be
the application reason for doing so?

I have also observed where pair of resistors of same value each one
end in each of the damping resistor PCB TH with other end of each
of this pair of resistors connected to each other with this
resistor pair common end connected to the PCB TH closest to input
terminal of bias resistor with no bias resistor. What application
configuration my this be for? Maybe fully differential vs PCB base
design maybe for bipolar?

Is the damping resistor use for a Lehman or LaCoste type
seismometer? Geophones tend to have damping resistor connected
across the geophone when purchased.

I assume for a Force Balance seismometer no matter make/model no
damping resistor is used.

I assume if differential then input via + and - terminals with GND
to shield at board (GND not connected at instrument to avoid ground
loops and RFI pickup). I assume for bipolar then GND connected to
input - with bipolar input signal connected to +. Are these both
correct?

If the input is +- 2.5V then I assume
<https://www.seismicnet.com/psnadc24/chan_sch.png> applies and
software needs to configured for 2.5V as 0V reference. Is this for
bipolar or differential? Is this where no resistors are populated
for voltage divider and with a 274K bias resistor?

It it correct the damping resistor applies where maybe needed for
geophone or replace one soldered on geophone and if needed for
Lehman, LaCoste, Hammerhead, et al coil/magnet type seismometers?

John L. Males
Toronto, Ontario
Canada

2026-07-24 22:39+0000 UTC eMail Start
2026-07-24 23:43+0000 UTC
2026-07-24 19:43-0400 EDT

*****Not GPG/PG Signed*****


On Date: Fri, 24 Jul 2026 10:17:48 -0700
From: Larry Cochrane <lcoc...@sonic.net>
To: psn...@googlegroups.com
Subject: Re: [PsnList] Question: PSN ADC24 Input Resistor
Configuration

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