TL;DR: When using Multi-instrument Mode (MiM), the input and output voltage ranges, input impedance, and input coupling are configured using the global set_frontend and set_output commands, rather than the per-instrument commands available in standalone mode.

Different Moku devices support different input and output voltage ranges. Table 1 summarizes the available ranges and their corresponding attenuation or amplification settings.

   - Note: On Moku:Delta, an input attenuation of –20 dB corresponds to an input amplification of +20 dB. This feature is unique to Moku:Delta.

When configuring inputs and outputs through the API, there are subtle but important differences between using standalone instruments and using MiM. In standalone mode, each instrument manages its own frontend settings. For example, the Oscilloscope controls its own input attenuation, and the Waveform Generator controls its own output gain.

In MiM, however, the frontend is shared across multiple instrument slots. This means the Waveform Generator no longer directly controls output gain, since users can dynamically remap its output channel to any physical DAC (or choose not to connect it to a DAC at all). Similarly, the Oscilloscope no longer directly controls input attenuation or range, because the same input may be shared by multiple instruments. To handle this, MiM provides global commands: set_frontend to configure input attenuation, impedance, and coupling, and set_output to configure output gain.

Moku:Go and Moku:Lab provide fixed output ranges. Moku:Go is limited to 10 Vpp into 1 MΩ, while Moku:Lab is limited to 2 Vpp into 50 Ω. In contrast, Moku:Pro and Moku:Delta include analog output amplifiers, which enable higher configurable output ranges. Table 2 summarizes the conceptual differences in how input and output voltage ranges are configured in standalone instruments vs. MiM.

   - Note: Starting from MokuOS firmware version 619, the set_frontend command (for both standalone instruments and MiM) uses an interchangeable gain parameter to configure input ranges. This parameter is equivalent to attenuation but expressed with opposite signs. For example, 20 dB attenuation corresponds to –20 dB gain.

   - Note: For more details on why some instruments use range while others use attenuation to configure the input range, see the API webpage.

For outputs in standalone instruments, configuration generally follows two approaches. Instruments with waveform generation capabilities adjust the output range automatically when the user defines an output amplitude, with the amplifier being enabled as needed. Other instruments provide a manual gain option, as seen in the Moku: app (Figure 1). In these cases, the API mirrors the app by allowing the user to explicitly configure the gain or select a range.

Figure 1. Example of a Moku instrument with a manual gain option to amplify output signals.