TouchDRO Adapter Feature Comparison

The current generation of TouchDRO scale interface adapters consists of two families:

Both families are based on the same powerful dual core 32-bit microcontroller and run the same version of the core firmware. All adapter models come with four high-speed differential scale inputs that work with single-ended (5V TTL) and differential (RS-422) quadrature encoders. This includes the majority of modern optical and magnetic DRO scales, as well as NPN, PNP, and push-pull rotary encoders.

Adapter Features

  TDA-420 TDK-400 TDK-40T TDK-40
  TouchDRO TDA-400/420 Adapter TouchDRO TDK-40/40T DIY Adapter Kit
  Comes fully assembled. Learn more Requires some soldering and mechanical assembly. Learn more
Total Inputs 6 4 4
RS-422/Differential Inputs 4 4
TTL/Single Ended Inputs 2 1 0 0
Reference Track Support Yes 2 No
Serial Protocol Decoding Mitutoyo SPC, BIN6 3 No
Tachometer Input 1 1 0 1 0
Probe/Height Setter Inputs 2 1 0 0 0
Limit Switch Inputs 4 1 0 0
Bluetooth Yes Yes
USB Full Time When Bluetooth is connected
Other Features
TouchDRO Version TouchDRO Plus TouchDRO Basic
Power Loss Position Retention Yes No
Over-the-Air Updates Yes No
Warranty 5 years 1 year

1 Two flexible TTL inputs can be user-configured as a combination of up to two encoder inputs, pair of probe inputs, tachometer input, or two pairs of limit switch inputs.
2Requires DRO scales with a compatible reference track.
3Requires a compatible signal converter module.

Technical Characteristics

  TDA-420/400 TDK-40/P/T
Position Refresh Rate 25Hz
Supply Voltage 5V-5.5V
Max Current Draw 300mA
Firmware Family ESP32 V3 Pro ESP32 V3 Lite
Primary Scale Inputs
Input Lines per Axis A, A', B, B', R/Z, R'/Z' A, A', B, B'
Encoder Support PNP, NPN, Push/Pull
Supply Voltage 5V
Min Signal Voltage 1.8V
Max Signal Voltage 5V
Max "Low" Signal Voltage 1.2V
Min "High" Signal Voltage 3.6V
Max Input Frequency 1MHz
Min Edge Separation 250ns
Glitch Rejection Yes
Reference Trigger Latency 2 µs N/A
Aux. Axis Inputs
Input Lines per Axis 2a 1b
Encoder Support NPN, Push/Pull
Supply Voltage 5V
Min Signal Voltage 2V
Max Signal Voltage 5V
Max Low Signal Voltage 1V
Pull up/down Pulled up to 5V
Max Quadrature Frequency 100KHz N/A
Min Quadrature Edge Separation 5 µs N/A
Glitch Rejection No N/A
Tachometer Pulses/Second 0.5-40,000
Max Probe Latency 2 µs N/A
Max Limit Switch Latency 2 µs N/A

aTDA-420 only
bTDK-40T only

Parameter Explanation

Position Refresh Rate

This is the frequency at which the given adapter sends the value to the application when the axis is in motion. For instance, the adapter from glass/magnetic scales will send the position 25 times per second, while the other two send the value only 10 times per second.

Max Frequency

Highest quadrature signal frequency that the input will be able to process; higher is better. Exceeding this frequency will lead to missed pulses. For example, a 1-micron scale moving at 1 meter per second will have quadrature frequency of 250KHz.

Min Edge Separation

Minimum pulse width that the adapter will register; lower is better.

Tachometer Pulses Per Second

This is the number of pulses per second the tachometer can recognize reliably. For instance, when a single mark encoder disk is used, the tachometer will read between 30 RPM and 600,000 RPM (1 pulse every 2 seconds to 10,000 pulses per second); with a disk that has 10 marks, the supported RPM range will be between 3RPM and 60,000 RPM.

Probe and Limit Switch Trigger Delay

This is the amount of time the adapter will take to capture the position after the probe or a limit switch is engaged. Lower is better. This is proportional to the potential digital "backlash" in the system. For instance, when the axis is moving at 1mm per second, 1µs delay will result in potential error of 0.000001mm; 100ms will result in 0.1mm potential error.

Max Signal Voltage

This is the highest safe signal level that can be applied to the given input. Voltage that is higher than the indicated level will quickly permanently damage the input and the board will need to be repaired.

Min Signal Voltage

This is the lowest voltage level that will be recognized by the given input. Any value above this level (up to the max voltage) will be treated as a logical 1.

Max Low Signal Voltage

This is the highest voltage level that will still be recognized as a logical 0 when the signal is going from high-to-low.