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Simulation Mode

Simulation mode lets you develop and test sequences without any physical hardware or NI-VISA installation. Every instrument driver returns physically plausible values with a small amount of Gaussian noise so sequences behave realistically.

When is Simulation Mode Active?

Simulation mode activates automatically in two cases:

  1. NI-VISA not installed — visa64.dll is not found in the standard NI installation path; the application falls back to simulation for all VISA resources.
  2. Explicit checkbox — the Use Simulation checkbox in the Connection Manager is checked; this forces simulation even when NI-VISA is present.

The status bar at the bottom of the main window shows VISA: Simulation when active.

Connecting a Simulated Instrument

  1. Click Add Instrument (+) in the left sidebar

  2. Click Refresh — the resource list shows one simulated entry per supported instrument type:

    Resource Intended driver
    SIM::GPIB0::22::INSTR (HP34401A) HP 34401A
    SIM::GPIB0::10::INSTR (Keithley2000) Keithley 2000
    SIM::GPIB0::09::INSTR (Agilent34970A) Agilent 34970A
    SIM::GPIB0::11::INSTR (ItechIT6922B) ITECH IT6922B
    SIM::TCPIP0::192.168.0.100::INSTR (RTB2004) R&S RTB2004
    SIM::TCPIP0::192.168.0.101::INSTR (RigolDS1000Z) Rigol DS1000Z
    SIM::COM3 (CTSChamber) CTS Chamber

  3. Select a resource, choose the matching driver, and click Connect

Tip

Any SIM:: resource works with any driver. The suggested pairings above are just for clarity. You can also type a custom resource string (e.g. SIM::INSTR) in the Manual Resource field.

Simulated Values per Instrument

Multimeters — HP 34401A, Keithley 2000

The simulated DMM tracks the last CONF: command and returns a realistic value for each function.

Function Command Simulated value
DC Voltage CONF:VOLT:DC 3.300 V ± 1 mV
AC Voltage CONF:VOLT:AC 1.500 V ± 5 mV
DC Current CONF:CURR:DC 125 mA ± 0.2 mA
AC Current CONF:CURR:AC 80 mA ± 0.2 mA
2-wire Resistance CONF:RES 1 000 Ω ± 0.5 Ω
4-wire Resistance CONF:FRES 1 000 Ω ± 0.5 Ω
Frequency CONF:FREQ 50.00 Hz ± 0.01 Hz
Period CONF:PER 20.00 ms ± 1 µs
Diode CONF:DIOD 652 mV ± 1 mV
Continuity CONF:CONT 5.2 Ω ± 0.1 Ω
Temperature (TC) CONF:TEMP 25.0 °C ± 0.1 °C

Burst measurements (SAMP:COUN N + FETCH?) return N independent samples, each with its own noise draw.

Data Acquisition — Agilent 34970A

The scan engine uses the same function-to-value table as the DMMs above. When a ROUT:SCAN (@...) command is received, the simulator counts the number of channels in the scan list. A subsequent FETCH? returns exactly that many comma-separated values, one per channel, using the currently configured function.

Example: scanning channels 101–103 after CONF:VOLT:DC → FETCH? returns:

+3.29987,+3.30101,+3.29954

DC Power Supply — ITECH IT6922B

The simulator maintains an internal voltage set-point and current limit. Measurement results reflect the configured values:

Query Returned value
VOLT? Voltage set-point (last VOLT x command)
CURR? Current limit (last CURR x command)
OUTP? 1 if output ON, 0 if OFF
MEAS:VOLT? Set-point ± 2 mV when output is ON; 0 when OFF
MEAS:CURR? ≈ 8 % of current limit ± 1 mA when ON; 0 when OFF
MEAS:POW? Simulated V × I product
STAT:OPER:COND? 1 (CV mode always assumed)

Simulated load

The 8 % current draw models a modest resistive load on the output. There is no simulated short-circuit or CC-mode transition.

OVP and OCP levels are stored and returned correctly by VOLT:PROT?, CURR:PROT:LEV?, and their STAT? companions.

Oscilloscopes — R&S RTB2004, Rigol DS1000Z

Parametric measurements — MEASn:RES:ACT?:

Measurement type Simulated value
Frequency 1 000.0 Hz ± 0.5 Hz
Period 1.000 ms ± 100 ns
Amplitude / Pk-Pk 2.00 V ± 10 mV
RMS 707 mV ± 3 mV
Mean / Vavg 0 V ± 2 mV
Rise / Fall time 10 ns ± 0.5 ns
Duty cycle 50.0 % ± 0.05 %
Phase 0.0 ° ± 0.1 °

Waveform readout — CHANn:DATA?:

Returns 1 000 ASCII-encoded samples of a 1 kHz sine wave with amplitude ≈ 1 V plus small noise (σ = 5 mV). The time axis is derived from the current timebase setting (TIM:SCAL):

Time span = TIM:SCAL × 10  (one full acquisition window)

The waveform header (CHANn:DATA:HEAD?) is computed to match:

−half_span, +half_span, 1000, 1

Channel scale (CHANn:SCAL) and timebase values are stored and returned correctly by their ? queries.

Environmental Chamber — CTS T-40/50

The chamber simulator maintains a continuously-updated actual temperature that tracks the set-point according to the configured ramp rates. This means sequences using CTS_WaitForTemperature will actually wait for the simulated temperature to converge.

Property Default
Initial temperature 23.5 °C
Default set-point 25.0 °C
Ramp-up rate 3 K/min
Ramp-down rate 3 K/min
Noise on each read ± 0.02 °C

Temperature dynamics: Every A0 query (read temperature) triggers an update. The actual temperature moves toward the set-point at the configured rate based on real elapsed wall-clock time between queries. If the chamber is not running (before CTS_ChamberStart), the temperature drifts slightly around its current value but does not track the set-point.

Example timeline with default 3 K/min ramp and set-point changed to 85 °C:

t=0 s   CTS_SetTemperature → 85 °C
t=0 s   ReadTemperature → 23.5 °C  (chamber just started)
t=60 s  ReadTemperature → 26.5 °C  (+3 K after 1 min)
t=600 s ReadTemperature → 53.5 °C  (+30 K after 10 min)
t=1233 s ReadTemperature → 85.0 °C (set-point reached)

The simulated chamber reports running (O → O101) and ramp active (R0 → R0 11 ...) once CTS_ChamberStart is executed.

How Noise is Generated

All noise values use the Box-Muller transform to produce a Gaussian (normal) distribution:

double u1 = 1.0 - rng.NextDouble();
double u2 = 1.0 - rng.NextDouble();
double noise = sigma * Math.Sqrt(-2.0 * Math.Log(u1)) * Math.Sin(2.0 * Math.PI * u2);

This gives realistic measurement scatter — occasional outliers included — rather than the flat uniform distribution that a plain NextDouble() would produce.

Limitations

  • No CV/CC transition for the power supply — the output is always in CV mode in simulation.
  • No fault conditions — no OVP/OCP trip, no instrument error states.
  • No waveform math — oscilloscope MATH channel queries return generic values.
  • No multi-instrument coupling — e.g., the power supply's simulated output voltage does not affect a simulated DMM connected in parallel.
  • Single-instance state — each SimulatedConnectionProvider holds its own state. Two simulated connections to the same SIM::GPIB0::22::INSTR resource string are independent.