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SMPL Standard

SMPL equipment in a lab setting.

SMPL is an open standard. That means Leeman Geophysical LLC is sharing the mechanical dimensions and electrical pinouts to allow interfacing to and from any other system as well as creation of your own custom interfaces.

Mechanical Footprint

SMPL boards are standardized to the full size (1S) and half size (0.5S) circuit board sizes. This standardization makes creating enclosures much easier as well as allowing standard mounting brackets, drill templates, and more to be used.

Mounting Holes

All mounting holes in SMPL circuit boards are 0.1285 inches (3.26 mm) in diameter. This allows for the use of both imperial #4 hardware as well as metric M3 hardware. The system is designed in the USA and imperial hardware is the preferred standard, but both imperial and metric are accommodated as imperial hardware can be difficult to obtain outside the USA.

Potentiometer Spacing

All adjustment potentiometers are spaced 0.3 inches from adjustment screw center to adjustment screw center unless the part required makes this impossible. The position of potentiometers on the circuit board is always on the top of the board facing the outward or front side. Positioning along the long axis is as-required.

1S (full size) SMPL circuit board dimensions.

1S (full size) SMPL circuit board dimensions.

0.5S (half size) SMPL circuit board dimensions.

0.5S (half size) SMPL circuit board dimensions.


The SMPL system is built around push on connectors from the Molex Picoflex PF-50 90325 family. These connectors are a micro blade style connector that is keyed to prevent reverse connections. Cables in many lengths as well as connectors of many different pin counts are available from this long time component manufacturer. The connectors have a space saving 0.05 inch (1.27 mm) pitch, yet are still rated for 1.2A and 250V.

Connector `pin 1' is marked on the PCB with a small round dot and is always on the side of the connector with the wider key post. To reduce confusion between numbered connectors such as D-Sub connectors, the simple connector pins are denoted with letters. Pin A (pin 1) counts up through the standard English alphabet towards the smaller key post on the connector.

Connectors are arranged if at all possible with:

  • Power on the left as viewed from the top.
  • Sensor inputs/outputs on the right as viewed from the top.
  • With adjacent connectors turned opposite ways with pin A towards the center line of the PCB to increase ease of connecting and disconnecting multiple cables.

Standard Pinouts

The pinouts of these connectors are standardized for different functions within the SMPL ecosystem. Some of these are necessary for many modules to work together (such as power connections) and others are standards established to help make all systems as similar as possible to help with interchangeability and troubleshooting (such as how a load cell is connected to a DB9 connector).

Analog Power (+/- 15 VDC Typ.)

Pin Description
A Ground
D Not Connected

Digital Power (3.3, 5 VDC Typ.)

Pin Description
A Ground
B 3.3 VDC
D Not Connected

Analog Signal (Single Ended)

Pin Description
A Ground
B Signal
C Not Connected
D Not Connected

Analog Signal (Differential)

Pin Description
A Ground
B + Input
C - Input
D No Connection

Note - optional jumper to connect C to ground making this equivalent to the single ended connector.


Pin Description
A - Excitation or Ground
B - Input
C + Excitation
D + Input

We love using DB9 connectors to interface a variety of sensors to our systems. They are inexpensive, robust, and work great for low frequency signals like many of those encountered in our labs and industrial environments. Now, with our DB9 breakouts, you can effortlessly connect any DB9 to any 4-pin SMPL device, expanding compatibility across your equipment.


Wire Color SMPL Pin DB9 Pin Description
Black A 4 GND
White B 8 -Input
Red C 2 Excitation
Green D 7 +Input
Shield S 3 Shield to Case GND

Load Cell

Wire Color SMPL Pin DB9 Pin Description
Black A 5 -Excitation(GND)
White B 9 -Input
Red C 1 +Excitation
Green D 6 +Input
Shield S 3 Shield to Case GND