REXDESK: log analogue and digital inputs

Record sensor voltages and on/off signals alongside your bus data, scaled to engineering units. This guide also shows how to wire a digital input.

Which loggers have inputs

REXGEN 2, REXGEN 2 IMU GNSS, REXGEN Air and REXGEN Pro have analogue and digital inputs. REXGEN 1 has none. REXGEN 2 has two analogue and two digital inputs. These guides give the input pins and their limits:

• REXGEN 2 and REXGEN 2 IMU GNSS: pinouts, LEDs and installation
• REXGEN Air: pinouts, harnesses, LEDs and installation
• REXGEN Pro: overview and specifications

Analogue inputs

1. Create a project. Select New Project on the toolbar.
2. Drop Analog on Channels. Drag Analog from the Channels group onto the Channels area of the configuration.
3. Set up the channel. In Add Analog Channel, select the input in Analog Channel. Enter the Sampling Rate (ms), which is the time between two samples.

   

4. Enter the scaling. REXDESK applies Formula: A*X + B. X is the input in volts, Coeff A is the slope or scale factor and Coeff B is the offset. Enter both coefficients. The logger records the result in your engineering units.
5. Add the channel. Select Add. The channel appears in the list. Repeat for each input.
6. Run the configuration. Select Run, then save and name the project. The logger loads the configuration and starts logging at once.

For example, a pressure sensor's output runs from 0 V at 0 bar to 5 V at 10 bar. That is a slope of 2 bar per volt and no offset. Enter A = 2 and B = 0 to record bar.

Digital inputs

1. Drop Dig In on Channels. Drag Dig In from the Channels group onto the Channels area.
2. Set up the channel. In Add Digital Channel, select the input in Digital Channel and enter the Sampling Rate (ms).

   

3. Add the channel. Select Add. Use the buttons beside the list to add another digital channel, edit one or remove it.
4. Run the configuration. Select Run, then save and name the project.

A digital input reads high when nothing is connected to it. To start or stop logging from a digital input, add a trigger. See REXDESK: start and stop logging with triggers.

Watch: Configure analogue and digital channels using REXDESK (1:15)

Wiring a digital input

A REXGEN digital input reads a voltage below 0.8 V as low and above 2.5 V as high. Three of the circuits below hold the input high through a 1 kΩ pull-up resistor, and the switch, the transistor or the relay contact pulls the input low when it switches on. The fourth uses a Schmitt-trigger buffer such as SN74LVC1G14, whose output drives the input directly from the instrumentation supply.

The pull-up needs a supply. Where it comes from depends on the logger:

Next: REXDESK: set up GNSS and the IMU.