Temperature

Built-in monitoring sensors

There are 10 built-in semiconductor temperature sensors. Each of these 10 sensors is placed under a culture chamber to precisely monitor its temperature.

These sensors are separate from the sensors used to control the temperature and can be used by a monitoring system creating an independent control channel.

All 10 sensors are connected to a Monitor-interface board. Output from this board is 4-20 mA current.

Sensor interface board is electrically isolated from the G210 Incubator Control system and has its own power supply.

Sensor and power supply connectors

The 10 individual 4-20 mA temperature sensor outputs are available on a 25 pin D-sub female connector J102 located on the rear of the incubator.

A corresponding D-sub male connector is supplied with the System (see Accessories).

The Monitor Interface Board must be supplied from 24VDC 500mA power supply which is delivered with the unit (see Accessories). It can be done by providing the power via a power connector J100. Alternatively +24V can be connected to pins 1-2 and GND to pins 24-25 of 25 pin D-sub connector.

Connection to 4-20 mA input

The unit presents the temperature using 10 x 4-20 mA current outputs. The system works optimal if the current converter input has a total resistance between 200 - 500 Ohm.

The 4-20 mA span corresponds approximately to a temperature range of 16 - 80°C so e.g. 9.25mA corresponds approximately to 37°C.

Low resistance converter input (Rinternal<200 Ohm)

If the current converter input resistance is lower than 200 Ohm then a resistor must be placed in series to increase the summary resistance to 200 - 500 Ohm range.

For example if a converter input resistance Rinternal = 60 Ohm, then a 140 to 440 Ohm Rseries resistor must be placed in series. It can be mounted inside the D-sub plug enclosure.

Reading the temperaturs using voltage input

It is possible also to read the values using a converter with voltage input.

Medium resistance converter input (500 OHM<Rinternal<500 kOhm)

If the receiver is a voltage measuring device with an input resistance of e.g 600 Ohm a resistor must be placed in parallel with the terminals so the resulting resistance is between 200 and 500 Ohm.

The best is to obtain 250 Ohm input resistance as this gives for 4-20 mA current range a voltage range of 1 to 5 V.

Then the input range of 16 to 80°C will be mapped to 1 to 5 V output.

Example:

The resulting resistance shall be 250 Ohm:

Then

1/RLoad = 1/250 -1/Rinternal

1/Rload = 1/250-1/600

Rload=430 Ohm

Use 0.1%, 0.5W resistor.

The 9.25 mA current which corresponds to 37°C will generate voltage drop of 250*9.25 = 2 312.5 mV = 2.31 V

High resistance converter input (Rinternal>500 kOhm)

If the voltage input resistance is higher than 500 kOhm then its influence in a parallel connection can be omitted and Rload = 250 ohm, 0.1%, 0.5W resistor must be placed in parallel with the terminals.

As before the input range of 16 to 80°C will be mapped to 1 to 5 V output.

B3 settings

If current ADC is used:

Input range 4-20 mA

Output range 16-80°C

Formula y=4*x

The formula will look much more complex in B3 but if you do the math this will be the final result.

If voltage ADC is used:

Input range 0-5 V

Output range 0-80°C

Formula y=4*x

In this case the readings are meaningful for voltages above 1 V (temperature above 16°C).