Multimeter usage

Updated 2 months ago ​by Jennes

This guide is made for experienced users. Before attempting this, first make sure that you have performed the Selftest and that you have checked MK3 EINSY miniRAMBo electronics wiring.

In many cases, we need to decide whether a component is faulty, or just wrongly installed. There are also situations where we need to decide which component exactly is to be replaced. We are using the multimeter (multitester) for checking continuity, measuring resistance values of heaters and thermistors, and measuring the voltage coming from the PSU and going to the heaters.If you don't have a multimeter, you can consider one that is similar to the ones below. The device does not have to be expensive ( USA, EU).

How to measure

To get started, we first have to properly connect the two measurement probe cables to the multimeter:

  • The black lead goes in the COM port.
  • The red lead goes in the port for Volts (V), Ohms (Ω) and Frequency (Hz).

Where to measure

For every component, there are several options, our main focus will be on the connectors.The measurement appears on the multimeter LCD as soon as the measurement probes touch the component. To obtain the correct and relevant values, this is where you need to apply the probes:

  • Thermistors: metal inserts in plastic connectors

  • Hot end heater: screws holding the cables in the connector

  • Heat bed: the solder pads/screws holding the wires on the heat bed (MK2/S) or screws holding the cables in the connector (MK3/S)

Fuses or wires

Fuses can be checked by using the continuity feature on a multimeter. The only thing that will be checked is whether the component is able to conduct signals or power or not. By touching each of the measurement leads of the multimeter to the other end of the fuse or wire, a signal (beep or 0 value on the multimeter screen) will indicate that the component is intact and therefore, should work.

The fuse for the PSU can be taken out of the slot above the power cord by using a flat head screw driver.

Heaters

Resistance
For this measurement, the printer has to be turned off and the component that is measured has to be unplugged from the RAMBO.

In order to check if heaters are within their range of specified resistance, the following measurement can be done. For this measurement, the multimeter needs to be set to the lowest range that includes 20Ω.

The measurement can be done on the screws in the connector for both the hot end heater and the heat bed. For the heat bed, it is also possible to probe the solder pads / screws holding down the cables.

The following values can be expected:

MK3

Hot end heater

[12.3 Ω - 15.1 Ω]

Heat bed

[3.5 Ω - 4.0 Ω]

MK2/S

Hot end heater

[3.1 Ω - 3.8 Ω]

Heat bed

[0.9 Ω - 1.1 Ω]

Voltage
For this measurement, the printer will be turned on and there will be a risk of shorting the circuit. Always make sure to keep + and - from touching each other!

In order to check if the correct voltage is being supplied to the heaters, the following measurement can be done. For this measurement, the multimeter needs to be set to the lowest range that includes 24V.

The measurement can be done on the screws in the connector for both the hot end heater and the heat bed. For the heat bed, it is also possible to probe the solder pads / screws holding down the cables. In this case, the connectors have to be connected to the RAMBO.

To measure, start preheating the printer to PLA and measure the component you are investigating.

The following values can be expected:

MK3

Hot end heater

[23.5V - 24.5V]

Heat bed

[23.5V - 24.5V]

MK2/S

Hot end heater

[11.5V - 13.5V]

Heat bed

[11.5V - 13.5V]

Thermistors

For this measurement, the printer has to be turned off and the component that is measured has to be unplugged from the RAMBO.

In order to check if thermistors are within their range of specified resistance, the following measurement can be done. For this measurement, the multimeter needs to be set to the lowest range that includes 100 kΩ.

The measurement can be done on the screws in the connector for both the hot end heater and the heat bed. For the heat bed, it is also possible to probe the solder pads / screws holding down the cables.

All thermistors are rated to be 100 kΩ at 25 °C. To be realistic, with a varying temperature between 20°C and 30°C, you can expect [80 kΩ - 125 kΩ]


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