Temperature measurement 287 the smallest cross-sectional area that can be used whilst maintaining the required robustness, to minimise heat conduction and achieve a rapid tem- perature response For hygienic reasons, probes are thinly coated with inert epoxy resin. Currently there is no real alternative to the use of an array of individual temperature sensors if data on temperature distribution are required For over 50 years temperature sensors attached to multi-point chart recorders have been used to obtain the temperature history of up to 24 positions and these systems are still common in many processing plants. To differentiate between the sensors on the charts, a range of methods including different colours, line types or numbers have been used As the number of sensors creases it becomes more and more difficult to identify individual sensors and/or ten perature values. If the sole purpose of the recordings is to show that all the temperatures remain within upper and lower limits then chart recording systems are more than adequate. In situations where a more detailed analysis of the data is required then they are being increasingly replaced by microprocessor-controlled data logging systems. Data loggers range from multisensor( typically 2-16 temperatures)ver- sions of the solid state instruments already mentioned, to sophisticated processing systems with thousands of measurement points Two types of portable logging systems are available. The larger type (approximately the size of a large paperback novel) has built in displays and buttons or switches to set start times time intervals between measure ments and to scan through, using the display, the temperatures, that have been measured Instruments can be purchased with between 2 and 16 plug in temperature sensors, and some will display the maximum, minimum and mean temperature recorded by a particular sensor. For more detailed analy- sis of the temperatures, the recorded data are transferred to a personal com puter. The PC is required to program the start time, recording interval and so on, and analyse the data with the smaller loggers. These instruments usually have a maximum capacity of 8 temperature sensors, l of which is often built into the instrument Developments in computer storage chips are continually extending the number of temperature values that can be held in both types of logger Modern instruments would typically be able to take readings of 4 tem- perature sensors at 5min intervals over a 2-3-week period. Further developments in electronics are extending the temperature range over which the instruments will operate. Some instruments will record accu- ately inside blast and spiral freezing systems whilst others can operate ambient temperatures up to 70-80C For extended use at sub-zero tem peratures special batteries are required. Logging systems have been devel- oped which use insulated heat resistant cases to allow operation for several hours at temperatures up to 300C. This allows measurement of product and processing temperatures in batch and continuous baking/cooking operations.the smallest cross-sectional area that can be used, whilst maintaining the required robustness, to minimise heat conduction and achieve a rapid tem￾perature response. For hygienic reasons, probes are thinly coated with inert epoxy resin. Currently there is no real alternative to the use of an array of individual temperature sensors if data on temperature distribution are required. For over 50 years temperature sensors attached to multi-point chart recorders have been used to obtain the temperature history of up to 24 positions and these systems are still common in many processing plants. To differentiate between the sensors on the charts, a range of methods including different colours, line types or numbers have been used. As the number of sensors increases it becomes more and more difficult to identify individual sensors and/or temperature values. If the sole purpose of the recordings is to show that all the temperatures remain within upper and lower limits then chart recording systems are more than adequate. In situations where a more detailed analysis of the data is required then they are being increasingly replaced by microprocessor-controlled data logging systems. Data loggers range from multisensor (typically 2–16 temperatures) ver￾sions of the solid state instruments already mentioned, to sophisticated processing systems with thousands of measurement points. Two types of portable logging systems are available. The larger type (approximately the size of a large paperback novel) has built in displays and buttons or switches to set start times, time intervals between measure￾ments and to scan through, using the display, the temperatures, that have been measured. Instruments can be purchased with between 2 and 16 plug￾in temperature sensors, and some will display the maximum, minimum and mean temperature recorded by a particular sensor. For more detailed analy￾sis of the temperatures, the recorded data are transferred to a personal com￾puter. The PC is required to program the start time, recording interval and so on, and analyse the data with the smaller loggers. These instruments usually have a maximum capacity of 8 temperature sensors, 1 of which is often built into the instrument. Developments in computer storage chips are continually extending the number of temperature values that can be held in both types of logger. Modern instruments would typically be able to take readings of 4 tem￾perature sensors at 5 min intervals over a 2–3-week period. Further developments in electronics are extending the temperature range over which the instruments will operate. Some instruments will record accu￾rately inside blast and spiral freezing systems whilst others can operate in ambient temperatures up to 70–80 °C. For extended use at sub-zero tem￾peratures special batteries are required. Logging systems have been devel￾oped which use insulated heat resistant cases to allow operation for several hours at temperatures up to 300 °C. This allows measurement of product and processing temperatures in batch and continuous baking/cooking operations. Temperature measurement 287